BIOTOPE AQUARIUM Model is an authentic re-construction of the original – often of a very small – aquatic biotope, which might disappear at any time without warning, or has already vanished. This little piece of Nature benefits the well-being of the aquarium inhabitants if:

• simulates BIOTOPE In NATURE
  
• replicates conditions of lake, creek or river
  
• has correct water type and chemical parameters
• provides a living space for the correct biological community
  
• applies the correct décor material

/bæŋk ˌvɛʤɪˈteɪʃən/

Bank vegetation refers to the plants growing along the edges of rivers, streams, ponds, or lakes. It includes grasses, reeds, shrubs, and trees that stabilize soil and interact with the aquatic ecosystem.

Ecological / Practical Relevance:
Bank vegetation provides shade, food (via leaf litter and insects), and shelter for fish. Its roots prevent erosion and influence water chemistry by releasing organic matter.

Example:
Riparian vegetation of Amazonian creeks — dominated by palms and shrubs — contributes to blackwater coloration through tannin release.

BAP Map or BIOTOPE AQUARIUM Project Map is the main instrument of the biotope mapping offered to beginners and experienced aquarists to build their own BIOTOPE AQUARIUM Model. Geographic map marks the GPS locations with the detailed aquatic biotope research and data on aquatic inhabitants that includes:

• original BIOTOPE In NATURE
• FISH and PLANTs found in this precise location
• other aquatic inhabitants
• water parameters
• substrate
• data on ecology

/ˌbʌɪə(ʊ)dʌɪˈvəːsᵻti/

Also called biological diversity, it indicates the variety of extant species in the environment and also encompasses the genetic variability within the species that form biological communities.

/ˈbaɪoʊˌfɪlm/

Biofilm is a slimy layer composed of microorganisms such as bacteria, algae, fungi, and protozoa adhering to submerged surfaces. It forms a micro-ecosystem crucial for nutrient cycling.

Ecological / Practical Relevance:
Biofilm serves as food for small fish, shrimps, and snails, aids in biological filtration, and stabilizes the microbial balance of aquatic environments.

Example:
In natural streams, Otocinclus catfish graze on biofilm covering stones and leaves.

/ˌbaɪoʊfɪlˈtreɪʃən/

Biofiltration is a biological water purification process where beneficial bacteria convert toxic nitrogen compounds (ammonia and nitrite) into less harmful nitrate through nitrification.

Ecological / Practical Relevance:
Essential in aquariums and natural systems, biofiltration maintains water quality and fish health by preventing ammonia buildup.

Example:
Bacteria of the genus Nitrosomonas and Nitrobacter colonize filter media, gravel, or plant roots, forming the biological backbone of filtration systems.

Example:
In natural streams, Otocinclus catfish graze on biofilm covering stones and leaves.

/baɪəˈlɒdʒɪkəl//kəˈmjuːnɪti/

A group of diverse species that occupy the same specific area and interact with each other. The overall structure of a community is determined by the diversity, the abundance and the specific interactions among the species within it.

/ˈbʌɪə(ʊ)təʊp/

From Greek bios (“life” or “organism”) and topos (“place”). A biotope is a limited area of uniform environmental conditions that provides living space for several organisms that coexist, interact, and cooperate, thus forming a biological community. Biotopes and the communities they host make up ecosystems that change constantly because of abiotic and biotic factors, but which are, nowadays, often threatened by human activity.

/ˈbʌɪə(ʊ)təʊp//əˈkwɛːrɪəm/

A biotope aquarium is an aquarium that replicates the natural biotope and ecosystem, where aquatic organisms, especially those threatened in the environment, can survive and adapt to a new home. For a biotope aquarium to be correct and replicating exactly the original habitat of the living species, organisms, environmental elements and conditions need to be selected accurately.

/ˈbʌɪə(ʊ)təʊp//ˈmæp.ɪŋ/

For fresh- and brackish water environments, biotope mapping allows a detailed description of the existing environment. A biotope is described as a habitat with its associated species assemblage and a detailed field survey allows the various biotopes present in an area to be identified and mapped.

A biotope is generally not considered to be a large-scale phenomenon. For example, a biotope might be a neighbouring park, a back garden, even potted plants or a fish tank on a porch. In other words, the biotope is not macroscopic but a microscopic approach to preserving the ecosystem and biological diversity.

/ˈblækwɔːtər/

Blackwater refers to darkly stained, acidic, and soft water found in tropical lowland rivers and forest streams. Its color comes from tannins and humic substances released by decaying vegetation.

Ecological / Practical Relevance:
Blackwater environments have low conductivity, low nutrients, and high biodiversity adapted to low-light and acidic conditions.

Example:
The Rio Negro basin (Amazon) is a classic blackwater system supporting Cardinal Tetra (Paracheirodon axelrodi) and Apistogramma species.

/bɹˈakɪʃwˌe‍ɪtə/

Brackish water is a broad term used to describe water, whose salinity is between that of fresh and marine water, and these are often transitional areas where such waters mix.

An estuary, which is the part of a river that meets the sea, is the best-known example of brackish water. Estuaries are highly variable environments because the salinity can change drastically over a relatively short distance, ranging from 10% to 32%, and over time of day due to tidal cycles – for example, high tide bringing saltier marine waters farther up into the estuary.

Seasonal increases in freshwater due to rainfall or snowmelt will decrease the salinity at a given point in the estuary. In order to survive here, resident microbes must be adapted to these large fluctuations in salinity. Despite this challenge, estuaries are very productive environments.

Brackish waters occur naturally as brackish groundwater in subsurface saline aquifers, as surface water due to natural erosion, or groundwater in coastal aquifers. Natural brackish water, particularly brackish groundwater, exists in most continents in quantities almost equal to or more than fresh groundwater and surface waters combined. Human activities can also cause fresh surface water and groundwater resources to become brackish through consumptive use and increase in their salt loading.

/ˈbriːdɪŋ bɪˈheɪvjər/

Breeding behaviour refers to the series of actions, rituals, and interactions performed by fish during the reproductive cycle — from courtship and mate selection to spawning, fertilization, and parental care. These behaviours are often complex and species-specific, shaped by evolutionary adaptation to their environment, reproductive strategy, and social structure.

Detailed description:
Breeding behaviour can include visual displays, body movements, colour changes, nest building, or sound production, all aimed at attracting mates and ensuring successful reproduction. In some species, males establish and defend territories, while in others, courtship occurs in groups or leks. Spawning may involve the release of eggs and sperm into open water (free spawners), attachment of eggs to specific substrates (substrate spawners), or the protection of eggs and fry in the mouth (mouth brooders).

Parental care is another important aspect and varies widely — from species that abandon eggs immediately after spawning, to those that guard, fan, or even carry offspring until they become independent.

Ecological and aquaristic relevance:
Understanding breeding behaviour helps aquarists create conditions that trigger natural spawning and ensure the survival of fry. It also provides insights into population dynamics, sexual selection, and habitat requirements in the wild.

Examples:

• Betta splendens constructs bubble nests and guards eggs aggressively (paternal care).
• Pelvicachromis pulcher forms monogamous pairs that guard fry together.
• Corydoras aeneus engages in group spawning, with little to no parental care.

/ˈbraʊnˌwɔːtər/

Brownwater refers to turbid water with a brown tint resulting from suspended sediments and dissolved organic matter. It is intermediate between clear and blackwater.

Ecological / Practical Relevance:
Common in floodplains where sediment and organic matter mix, creating habitats rich in plankton and nutrients.

Example:
Brownwater tributaries of the Amazon, like the Madeira River, host diverse species such as Satanoperca jurupari and Heros efasciatus.

/ˈbʌfər kəˈpæsɪti/

Buffer capacity, also known as alkalinity or acid-neutralizing capacity, refers to the ability of water to resist changes in pH when acids or bases are introduced. It represents the concentration of dissolved ions (mainly bicarbonates, carbonates, and hydroxides) that neutralize excess hydrogen (H⁺) or hydroxide (OH⁻) ions, thereby stabilizing the chemical balance of aquatic environments.

Detailed Description:
In aquatic ecosystems, pH stability is essential for the survival of fish, plants, and microorganisms. A high buffer capacity means that water can absorb acidic or basic substances without significant change in pH, providing a stable environment. Conversely, low buffer capacity (common in soft or blackwater habitats) means that even small additions of acids or bases can cause rapid and harmful pH fluctuations.

The buffering process in most freshwater systems is primarily governed by the carbonate–bicarbonate equilibrium:

CO2+H2O↔H2CO3↔H++HCO3−\text{CO}_2 + \text{H}_2\text{O} \leftrightarrow \text{H}_2\text{CO}_3 \leftrightarrow \text{H}^+ + \text{HCO}_3^-CO2​+H2​O↔H2​CO3​↔H++HCO3−​

This natural chemical system helps maintain a stable pH, especially in waters with moderate hardness.

Measurement and Units:
Buffer capacity is usually measured as carbonate hardness (KH), expressed in degrees (°dKH) or milligrams per liter (mg/L) of CaCO₃ equivalent.

• 1 °dKH ≈ 17.86 mg/L CaCO₃

In the aquarium context, a KH value between 3–8 °dKH ensures good pH stability for most species. Blackwater or rainforest biotopes may naturally have KH values close to 0–1 °dKH, which results in a more acidic but chemically delicate environment.

Ecological and Aquaristic Relevance:

• In natural habitats, buffer capacity influences species distribution, plant growth, and microbial activity.
• In aquariums, maintaining proper KH prevents dangerous pH crashes that can stress or kill sensitive species.
• Understanding the buffering system is essential when replicating specific biotopes, such as soft, tannin-rich blackwaters (low buffer) or hard, alkaline rift lakes (high buffer).

Examples:

• Amazon blackwater rivers (e.g., Rio Negro): Extremely low buffer capacity; pH often between 4.0 and 5.0.
• African Rift Lakes (e.g., Lake Tanganyika): Very high buffer capacity; pH around 8.5–9.0, highly stable.
• Central European streams: Moderate buffer capacity; pH near neutral (6.8–7.4).

/kɑː^rˈnɪvərəs/

Carnivorous fish have a meat-based diet which can include insects, other fish, and other invertebrates. They usually have different body structures, for example they can have a larger mouth, larger teeth and a more aerodynamic body for quickly swimming through the water. Some carnivorous fish are active hunters that will chase down their preys, like sharks; others wait for the prey to come to them, also in the deepest parts of the ocean. Some other species, like catfish or loach, resort to scavenging and catch all the food that has sunk to the bottom.

Common carnivorous aquarium fishes are some types of cichlid, arrowana, and piranhas. They should be regularly offered live food and frozen food, like feeder fish, brine shrimp, mosquito larvae, worms, mollusks, and other invertebrates.

/ˈkævɪti ˈspɔːnər/

A cavity spawner is a fish that deposits its eggs inside natural or artificial cavities such as holes, shells, rock crevices, or submerged logs.

Detailed Description:

• Males often guard the cavity or prepare it to attract females.
• Cavity spawning protects eggs from predators and turbulent water flow.
• Parental care varies by species; in some, both parents guard eggs and fry.

Ecological / Aquaristic Relevance:

• In aquariums, providing appropriate caves or hollow decorations is essential for encouraging natural breeding.

Example:

• Apistogramma cacatuoides deposits eggs on the roof of a rock cavity.
• Shell-dwelling Neolamprologus multifasciatus in Lake Tanganyika use snail shells as spawning sites.

CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) is a global agreement among governments, adopted in 1975 in order to regulate or ban international trade in plant or animal species that are under threat and safeguard their survival.

/kīˈränəməs/

The Chironomidae are a large family distributed worldwide, with more than 130 genera and 700 species in North America alone. They are often mistaken for adult mosquitoes but lack the long proboscis and are unable to feed on blood. Adults are short-lived, living only a few days to several weeks. Some imbibe honeydew and other natural sugars, but some take no food at all as adults.

Adult chironomid midges are 1–10 mm long, with slender legs, narrow, scaleless wings, and plumose antennae in the adult males.

Most chironomid larvae are aquatic or semiaquatic and construct tubes in, or attached to, the substrate. They are often the most abundant benthic organisms and occur in all types of habitats, including rivers, streams, lakes, ponds, water supplies, and sewage systems.

Chironomid larvae are cylindrical and have paired prolegs on the prothoracic and last abdominal segments. The head is heavily sclerotized and nonretractile. They have no spiracles. Many species, however, have a hemoglobin-like substance in their hemolymph and are called bloodworms because of their pink or red color. Most species are detritus feeders that graze on aquatic substrates. Others filter drifting food particles from the water with strands of saliva or are predators on other chironomid larvae or oligochaete worms.

They constitute a very high protein food, very welcome by all omnivorous and carnivorous fish, but obviously not suitable for vegetarian ones. Growing at home does not present many problems, as you can read below; the risk is that of introducing into the tank, together with the live food, other undesirable creatures, such as larvae of other insects, or parasites that can transmit to the fish.

Frozen bloodworms are a little safer from this point of view, although they are not entirely free from these risks, so they should be bought in reliable shops, where you can be relatively sure that the cold chain has not been interrupted. Frozen bloodworms must be rinsed thoroughly before giving it to the fish.

Chlorosis is a yellowing of normally green leaves due to a lack of chlorophyll. Many factors, singly or in combination, contribute to chlorosis. In northern Illinois, some of the most common causes among trees and shrubs include nutrient deficiencies related to soil alkalinity (high pH), drought, poor drainage, and compaction of the soil. Common tree species exhibiting chlorosis are pin oak, red maple, white oak, river birch, tulip tree, sweet gum, bald cypress, magnolia, and white pine.

/siː oʊ tuː ɪnˈdʒɛkʃən/

CO₂ injection is the deliberate introduction of carbon dioxide into an aquarium to enhance plant photosynthesis and control pH.

Detailed Description:

• Injected CO₂ dissolves in water, forming carbonic acid, slightly lowering pH.
• Promotes healthy plant growth, richer coloration, and faster tissue development.
• Must be carefully monitored to avoid CO₂ overdosing, which can reduce oxygen levels and harm fish.

Ecological / Aquaristic Relevance:

• Essential in heavily planted tanks or biotopes replicating dense vegetation streams.
• Combined with lighting and fertilization, CO₂ injection improves overall ecosystem stability in aquaria.

Example:
Pressurized CO₂ systems with a diffuser are standard in Dutch-style aquascapes.

CO₂ requirements:

/ˌkɒnsnˈtreɪʃn//ɒv//ˈsɛdɪmənts/

The presence of sediments in the water can be measured: the ratio of the dry sediment in a mixture of water and sediments/ the total weight of the mixture.

Waters with a high concentration of sediments are usually turbid.

/kɒndʌkˈtɪvɪti/

Conductivity range describes the ability of water to conduct an electrical current, which is directly related to the concentration of dissolved ions (salts and minerals).

Detailed Description:

• Measured in μS/cm (microsiemens per centimeter).
• Indicates water hardness, mineral content, and ionic composition.
• Natural waters:
  • Blackwater: 10–50 μS/cm (very soft)
  • Brownwater: 50–200 μS/cm (moderately soft)
  • Rift lakes: 300–600 μS/cm (hard)

Ecological / Aquaristic Relevance:

• Fish and plants are adapted to specific conductivity ranges.
• Sudden changes in conductivity can stress or kill sensitive species.

Example:

• Astyanax mexicanus thrives in 50–150 μS/cm water, typical of soft, slightly mineralized streams.

/krɪˈpʌskjʊlər ækˈtɪvɪti/

Crepuscular activity refers to a behavioural pattern in which organisms are most active during twilight periods, specifically at dawn and dusk, with reduced activity during full daylight and nighttime.

In aquatic ecosystems, crepuscular activity is common among fish species inhabiting shaded waters, forest streams, floodplains, and structurally complex habitats, where light levels change rapidly. This activity pattern allows species to exploit transitional light conditions.

Ecological significance of crepuscular activity includes:

• reduced predation risk, as visibility is lower for visual predators;
• access to prey species that are also active during twilight;
• optimisation of energy efficiency by balancing foraging success and safety;
• temporal niche partitioning between diurnal and nocturnal species.

In natural biotopes, crepuscular behaviour is influenced by light intensity, water turbidity, habitat structure, and seasonal day-length variation.

In biotope aquarium keeping, recognising crepuscular activity helps in:

• designing gradual lighting transitions rather than abrupt on/off cycles;
• providing appropriate cover and shaded microhabitats;
• correctly interpreting species behaviour that may appear inactive during peak daylight.

/ˈkʌrənt vəˈlɒsɪti/

Current velocity refers to the speed of water movement in rivers, streams, or aquariums, usually measured in m/s.

Detailed Description:

• Determines oxygenation, sediment transport, and habitat selection for aquatic species.
• Some fish prefer slow backwaters, while others inhabit fast-flowing riffles.
• Velocity interacts with substrate, vegetation, and dissolved oxygen, shaping ecosystem structure.

Ecological / Aquaristic Relevance:

• In aquariums, flow rate must replicate natural habitats to support species-specific behavior and reduce stress.

Example:

• Corydoras species prefer gentle currents (<0.1 m/s).
• Astyanax species occupy moderate flows (0.2–0.5 m/s) for schooling and feeding.

/ˈsaɪklɪŋ/ (tæŋk saɪkl/)

Tank cycling is the process of establishing a stable population of beneficial bacteria in an aquarium to convert ammonia → nitrite → nitrate, making the water safe for fish.

Detailed Description:

• Involves the growth of nitrifying bacteria (Nitrosomonas, Nitrobacter).
• Usually takes 4–8 weeks in a new tank.
• Essential for biological filtration and maintaining water quality.

Ecological / Aquaristic Relevance:

• Prevents toxic ammonia and nitrite accumulation.
• Required before introducing sensitive or juvenile fish into a new aquarium.

Example:

• Cycling with a small number of hardy fish (Danio rerio) or ammonia dosing allows bacteria to colonize the filter and substrate.

/sɪˌprɪnɒdɒnˈtɪfɔːrmiz ˈhæbɪtæt/

Refers to the natural habitats of fish in the order Cyprinodontiformes, which includes killifish, livebearers, and pupfish.

Detailed Description:

• Typically found in freshwater or brackish waters, including rivers, streams, ponds, and ephemeral pools.
• Habitats often feature vegetation, shallow waters, seasonal drying, or fluctuating parameters.
• Many species are annual fish, adapted to survive dry periods as eggs.

Ecological / Aquaristic Relevance:

• Knowledge of natural habitat helps reproduce water parameters, substrate, and seasonal cycles in aquariums.
• Essential for breeding and long-term survival of sensitive species.

Example:

• Nothobranchius furzeri inhabits ephemeral savanna pools in Africa.
• Poecilia reticulata thrives in moderately hard, flowing tropical streams.

/dɪˈkɒmpoʊzərz/

Decomposers are organisms that break down dead organic matter, including plant litter, animal remains, and waste products, into simpler substances that can be recycled in the ecosystem.

Detailed Description:

• Decomposers include bacteria, fungi, protozoa, and certain invertebrates.
• They convert complex organic molecules into nutrients such as nitrates, phosphates, and carbon compounds, which are essential for primary production by plants and algae.
• Decomposition occurs via chemical digestion and enzymatic breakdown, often accelerating in warm, oxygenated, and moist conditions.

Ecological / Aquaristic Relevance:

• Decomposers maintain water quality and nutrient cycles in natural habitats and aquariums.
• In aquaria, decomposer activity is observed in substrates, leaf litter beds, and biological filters.
• A healthy decomposer community prevents organic waste accumulation that could otherwise produce toxic ammonia or hydrogen sulfide.

Example:

• Bacteria in substrate biofilms break down uneaten food and plant debris.
• Asellus aquaticus (freshwater isopod) feeds on decaying leaves and contributes to nutrient cycling.

/dɪˌsɪˈkeɪʃən ˈpɪriəd/

The desiccation period is the time during which a water body dries up or significantly loses water, creating temporary terrestrial conditions.

Detailed Description:

• Common in ephemeral ponds, seasonal pools, and floodplains.
• Many aquatic species have evolved strategies to survive desiccation, such as dormant eggs, burrowing, or migration.
• Duration varies with climate, season, and geographic location.

Ecological / Aquaristic Relevance:

• Critical for annual killifish (Nothobranchius, Aphyosemion) whose eggs survive in dry substrate until the next wet season.
• In aquaria, simulating wet-dry cycles may be necessary for breeding certain ephemeral pool species.

Example:

• African savanna pools dry completely for 3–6 months; only desiccation-resistant eggs of Nothobranchius furzeri survive until rains return.
  

|dɪˈtrʌɪtəs|

Detritus can be defined as dead organic materials from any trophic level from the ecosystem. Most of the detritus occurring in sediments are derived from dead plankton and decaying plankton blooms. It is also made up of the decomposing remains of organisms and plants, and also of feces.

/dɪˈtrɪtɪvɔːr/

A detritivore is an organism that feeds primarily on detritus, i.e., decomposing organic matter, including dead plant material, feces, and decaying animal tissue.

Detailed Description:

• Detritivores play a key role in nutrient recycling by breaking down organic matter into smaller particles suitable for decomposers.
• Many detritivores are benthic or substrate-dwelling, feeding continuously to maintain sediment turnover.

Ecological / Aquaristic Relevance:

• Detritivores help clean substrates, reduce organic build-up, and support secondary production in both natural and aquarium ecosystems.
• Essential for biotope aquariums aiming to replicate natural benthic food chains.

Example:

• Corydoras catfish, freshwater shrimps (Caridina, Neocaridina), and aquatic worms are common detritivores in aquaria.

/dɪˈzɒlvd/ /ˈɒksᵻdʒ(ə)n/

It measures how much oxygen is found in the water. The presence of oxygen in the water is a positive indicator of quality, while its absence could be a sign of pollution. Sources of dissolved oxygen can be atmosphere, aeration and photosynthesis from algae and aquatic plants.

/ˌdɪstrɪˈbjuːʃən reɪndʒ/

The distribution range of a species is the geographic area in which it naturally occurs, including its habitat types, elevation, and biogeographic limits.

Detailed Description:

• Range can be localized, regional, or global, depending on ecological tolerance and dispersal ability.
• Includes native populations and, in some cases, introduced populations.
• Influenced by climate, water chemistry, substrate, vegetation, and interspecies competition.

Ecological / Aquaristic Relevance:

• Knowledge of distribution range helps replicate natural habitats in aquaria and determine suitable water parameters and temperature.
• Important for conservation status assessments and understanding species resilience.

Example:

• Astyanax mexicanus: Native to rivers and caves of northeastern Mexico and southern USA.
• Nothobranchius furzeri: Endemic to ephemeral savanna pools in Mozambique and Zimbabwe.

/daɪˈɜːrnəl ækˈtɪvɪti/

Diurnal activity refers to a behavioural pattern in which organisms are primarily active during daylight hours and inactive or less active during the night.

In fish and other aquatic organisms, diurnal activity is common in habitats with sufficient light availability, such as open rivers, lakes, floodplains, and clear-water systems. Diurnal species often rely heavily on vision for feeding, social interaction, and predator avoidance.

Ecological significance of diurnal activity includes:

• efficient exploitation of visually detectable food resources;
• synchronisation with daytime environmental cues, such as light intensity and temperature;
• interaction with other species through social behaviour, territoriality, and schooling;
• temporal separation from nocturnal species, supporting niche partitioning.

In natural biotopes, diurnal activity patterns are shaped by light regime, water clarity, habitat structure, and predation pressure.

In biotope aquarium keeping, understanding diurnal activity is important for:

• designing appropriate lighting schedules;
• observing natural behaviour and coloration;
• selecting compatible species with similar activity rhythms.

/ˈdɒmɪnənt//ˈspiːʃiz/

The tallest plant species present at a site.  There must be several individuals of the same plant present at one site for it to be the dominant species.

/ˈhæbɪtæt ˌfræɡmənˈteɪʃən/

Habitat fragmentation refers to the process by which large, continuous habitats are broken into smaller, isolated patches, often due to natural events or human activities such as damming, deforestation, or urbanization.

Detailed Description:

• Fragmentation affects species distribution, genetic diversity, and ecological interactions.
• Isolated populations may suffer from inbreeding, reduced food availability, and higher predation.
• Connectivity between fragments is critical for migration, breeding, and recolonization.

Ecological / Aquaristic Relevance:

• Understanding fragmentation helps aquarists replicate isolated or connected habitats for breeding programs.
• Guides conservation of sensitive or endangered species.

Example:

• Amazon floodplain deforestation creates fragmented fish habitats, affecting migratory species like Prochilodus.
• Small isolated ponds may house unique populations of Nothobranchius annual fish.

/ˈhɑːrdnəs/

Total hardness (GH, general hardness) measures the concentration of divalent cations, mainly calcium (Ca²⁺) and magnesium (Mg²⁺), in water.

Detailed Description:

• Expressed in mg/L CaCO₃ or °dGH.
• Influences water chemistry, buffering capacity, and fish osmoregulation.
• Soft water (<4 °dGH) is common in blackwater rivers; hard water (>12 °dGH) occurs in karst rivers and rift lakes.

Ecological / Aquaristic Relevance:

• Fish and plants are adapted to specific hardness ranges.
• Maintaining appropriate GH in aquaria ensures healthy growth, reproduction, and osmoregulation.

Example:

• Apistogramma species prefer soft water (2–6 °dGH).
• Rift lake cichlids (Neolamprologus) thrive in hard water (10–20 °dGH).

/ˈhɛdwɔːtər/

Headwaters are the source or upper reaches of a river or stream, typically small, clear, and fast-flowing.

Detailed Description:

• Often found in mountainous or elevated areas.
• Characterized by low nutrient content, high oxygenation, and cooler temperatures.
• Critical for downstream water quality and ecosystem health.

Ecological / Aquaristic Relevance:

• Fish adapted to headwaters often require well-oxygenated, flowing water in aquaria.
• Replicating headwater conditions is important for species like trout, characins, and rasboras.

Example:

• Upper streams of the Rio Negro in Brazil house small characins adapted to headwater conditions.
• European Phoxinus species inhabit cool, oxygen-rich headwater streams.

/hjuːˈmɪdɪk ˈæsɪd/

Humidic acid refers to a group of naturally occurring organic acids produced during the decomposition of plant material, especially leaves, wood, and other terrestrial vegetation entering aquatic ecosystems. It is a major component of humic substances, together with fulvic acids and humins.

Humidic acids are especially abundant in leaf litter zones, forest streams, swamps, and blackwater environments, where large amounts of organic matter undergo microbial breakdown.

From an ecological and chemical standpoint, humidic acids play several important roles:

• they contribute to lowering and stabilising pH, particularly in soft-water environments;
• they chelate metals and minerals, influencing nutrient availability and water chemistry;
• they impart a yellow to dark brown coloration to the water, characteristic of blackwater systems;
• they can reduce light penetration, affecting primary production and habitat structure.

In natural habitats, humidic acids help shape the physiological adaptations and behaviour of many fish and invertebrate species, often providing mild antimicrobial and stress-reducing effects.

In biotope aquaria, humidic acids are introduced through the use of leaf litter, driftwood, peat, and other botanical materials, or via natural extracts, to recreate authentic chemical conditions found in humic-rich freshwater ecosystems.

/ˌhaɪdrəˈɡræfɪk ˈnɛtwɜːrk/

A hydrographic network is the system of interconnected rivers, streams, lakes, and wetlands within a drainage basin.

Detailed Description:

• Determines water flow, sediment transport, and nutrient distribution.
• Supports biodiversity by connecting habitats for migration and reproduction.
• Includes main channels, tributaries, and floodplains.

Ecological / Aquaristic Relevance:

• Knowledge of hydrographic networks helps design biotope aquaria that mimic connectivity or isolation.
• Important for conservation planning and species introduction programs.

Example:

• The Amazon hydrographic network connects hundreds of tributaries supporting migratory fish like Prochilodus and Pseudoplatystoma.
• Rhine River network in Europe supports multiple freshwater species across connected streams and floodplains.

/haɪˈdrɒlədʒɪkəl ˈsaɪkəl/

The hydrological cycle (water cycle) is the continuous movement of water through the atmosphere, land, and aquatic systems.

Detailed Description:

• Includes evaporation, condensation, precipitation, infiltration, groundwater flow, and runoff.
• Drives water availability, seasonal flooding, and habitat dynamics.
• Influences aquatic chemistry and temperature.

Ecological / Aquaristic Relevance:

• Understanding the hydrological cycle is crucial for replicating seasonal water level fluctuations in biotope aquaria.
• Guides annual fish breeding, especially for species in ephemeral pools.

Example:

• Seasonal rainfall in African savannas triggers the hydrological cycle, creating temporary pools for Nothobranchius.
• Amazonian floodplains follow predictable cycles affecting spawning of migratory characins.

/ˈhaɪdrəˌfaɪt/

Hydrophytes are plants adapted to grow in water or saturated soils, either submerged, floating, or emergent.

Detailed Description:

• Include submerged macrophytes, floating-leaved plants, and emergent species.
• Adaptations: aerenchyma tissue for oxygen transport, flexible stems, and reduced cuticles.
• Provide oxygen, shelter, and spawning sites for aquatic fauna.

Ecological / Aquaristic Relevance:

• Essential for replicating natural aquatic habitats in biotope aquaria.
• Influence water chemistry, nutrient cycling, and microhabitat diversity.

Example:

• Submerged: Ceratophyllum demersum
• Floating: Lemna minor
• Emergent: Sagittaria sagittifolia

/ɪɡɑːˈpəʊ/

In central Amazonia the prevailing floodplain forest is differentiated into nutrient-rich white water “várzea” and nutrient-poor blackwater or clear water “igapó”.

The vast areas of igapó forests – seasonally flooded forests for extended periods (4-10 months) on blackwater (and clearwater) river/lake margins, – are the home to innumerous endemic species of plants and animals.

The black-water and clear-water rivers carry low loads of suspended matter and solutes, resulting in a scarcity of nutrients. These rivers have brown- or tea-colored waters, the color being the result of high concentrations of humic substances and organic acids suspended in the water.

Igapó forests mostly occur along black and clear water rivers that drain the Paleozoic and/or Precambrian shields of Guyana and Central Brazil. The floodplain of these rivers covers an area of approximately 200.000km² from which the most part is covered by close canopy forest.

The largest clear water rivers are the Xingu, Tapajós and Trombetas whose floodplains cover approximately 67.000km², while the main example of blackwater river is the Negro River, whose floodplains cover ∼118.000km², supporting the largest black-water inundation forest in the world.

Blackwater igapó: the balckwater system, represented by the Rio Negro basin, originated on the Precambrian shield of the northern region of the Amazon basin. Its transparent red-brown color originates from a high content of dissolved humic and tannin substances, which is about 10 times higher than in the Solimões/Amazon River.

The water is poor in nutrients and electrolytes with dominance of sodium among the major cations, presenting low alcalinity. The pH and electrical conductivity values are less than 5.0 and 25 µS/cm-1, respectively. The black color and acidity of the water are due to the elevated concentrations of dissolved organic material such as humic and fulvic acids.

Clearwater igapó: the rivers of the clearwater type have their upper catchments in the Central Brazilian and Guiana Archaic/Precambrian shields and are charachterized by pH values that vary between 5.0 and 7.0 and electrical conductivity in the range of 10-53.6 µS/cm-1. The water transparency can reach up to 355cm or still higher; but transparency values less than 100cm are also common in these rivers.

/ˈɪnˌfloʊ/

Inflow is the entry of water into a system from rivers, streams, springs, or precipitation.

Detailed Description:

• Determines water level, current velocity, nutrient input, and oxygenation.
• Influences habitat characteristics and species distribution.

Ecological / Aquaristic Relevance:

• Mimicking natural inflow in aquaria ensures oxygenation and water renewal.
• Important for seasonal breeding cues in certain fish.

Example:

• Rain-fed inflow in ephemeral pools triggers spawning of Nothobranchius killifish.
• Spring inflow maintains stable conditions for Astyanax mexicanus.

/ˌɪntərˈtaɪdəl zoʊn/

The intertidal zone is the coastal area between high and low tide marks, regularly submerged and exposed.

Detailed Description:

• Organisms must tolerate fluctuating salinity, temperature, and moisture.
• Includes sandy beaches, rocky shores, and mangroves.
• Biodiversity is high due to the variety of microhabitats.

Ecological / Aquaristic Relevance:

• Relevant for euryhaline or tide-adapted species in aquaria.
• Guides substrate choice, salinity variation, and tidal simulation.

Example:

• Mudskippers (Periophthalmus) and fiddler crabs inhabit intertidal zones.

/ɪnˈveɪsɪv//ˈeɪliən//ˈspiːʃiːz/

An Invasive Alien Species (IAS) is a species, subspecies, or lower taxon—plants, animals, fungi, or micro-organisms—that has been introduced, either intentionally or accidentally, outside its natural past or present distribution. IAS are those alien species whose introduction and/or spread threaten biological diversity, ecosystem functions, native species, human health, or economic interests.

Key aspects:

• The species is non-native in the new environment.
• It can survive, reproduce, and establish stable populations (naturalisation).
• It spreads or increases in abundance.
• It causes negative impacts (ecological, economic, health).

Pathways of Introduction

• Pet/aquarium trade
• Intentionally for ornamentation, food, biological control
• Accidental transport (ballast water, hulls, gear, trade of goods)
• Habitat modification & climate change facilitating spread

Why IAS Matter in Freshwater Systems
Freshwater ecosystems are particularly vulnerable because they are fragmented, have high biodiversity, and species often have narrow ecological tolerances. Introduction of IAS can:

• Outcompete native plants and animals
• Alter habitat structure (e.g. shading, blocking light)
• Disrupt nutrient cycles and water quality
• Introduce new diseases or predators
• Cause declines or extinctions of endemic species

Fifteen Notorious Freshwater Invasive Alien Species

Here are 15 freshwater IAS with proven high impact globally:

1. Zebra mussel (Dreissena polymorpha) – filters water heavily, alters food webs
2. Water hyacinth (Eichhornia crassipes) – forms dense mats, reduces oxygen and light
3. Giant Salvinia (Salvinia molesta) – floating plant forming thick mats
4. Bighead carp (Hypophthalmichthys nobilis) – competes with native fish for plankton
5. Silver carp (Hypophthalmichthys molitrix) – voracious filter feeder, disrupts ecosystems
6. Grass carp (Ctenopharyngodon idella) – overgrazes aquatic vegetation
7. Round goby (Neogobius melanostomus) – outcompetes native benthic fish
8. Golden Apple Snail (Pomacea canaliculata) – voracious herbivore, damages crops and native plants
9. Hydrilla (Hydrilla verticillata) – submerged plant forming thick mats
10. Water lettuce (Pistia stratiotes) – floating plant, blocks sunlight, reduces oxygen
11. New Zealand mud snail (Potamopyrgus antipodarum) – reproduces rapidly, competes with native invertebrates
12. Chinese mitten crab (Eriocheir sinensis) – burrows banks, spreads disease
13. Yellow floating heart (Nymphoides peltata) – dense floating pads shade native flora
14. Brazilian elodea (Egeria densa) – submerged plant smothering native vegetation
15. Northern snakehead (Channa argus) – predatory fish, aggressive, threatens native fish

/ɪnˈvəːtᵻbrət/

An invertebrate is an animal that lacks a vertebral column and, thus, does not belong to the chordate subphylum Vertebrata. Generally, invertebrate animals are soft-bodied, lacking a rigid internal skeleton for the attachment of muscles. Some of them, however, possess a hard outer skeleton that protects the body.

Invertebrates make up more than the 90% of all living animal species, such as sea stars, sea urchins, earthworms, sponges, jellyfish, lobsters, crabs, insects, spiders, snails, clams, and squid.

/ɪnˈvɜːrtəbrət ˈɡreɪzər/

An invertebrate grazer is an organism without a backbone that feeds on algae, biofilm, or periphyton.

Detailed Description:

• Includes snails, shrimps, amphipods, and insect larvae.
• Grazer activity controls algae growth and contributes to nutrient cycling.

Ecological / Aquaristic Relevance:

• Essential for substrate cleaning and maintaining ecological balance in biotope tanks.
• Supports microfauna diversity.

Example:

• Neocaridina shrimps graze algae in freshwater aquaria.
• Planorbella snails clean surfaces in slow-moving rivers.

IUCN (International Union for Conservation of Nature and Natural Resources) is an organization founded in 1948 whose aim is to influence, encourage, and assist societies to conserve the integrity and diversity of nature,and ensure that any use of natural resources is equitable and ecologically sustainable.

IUCN has drafted a Red List Categories and Criteria that is intended to be an easily and widely understood system for classifying species at high risk of global extinction. Species are divided into the followng categories:

• Not Evaluated (N/E);
• Data Deficient (DD): a taxon about which there is no adequate information to make an assessment about its endangerment;
• Least Concern (LC): a taxon that does not qualify as endangered;
• Near Threatened (NT): a taxon close to qualifying for a threatened category;
• Vulnerable (VU): taxons considered to be facing high risk of extinction in the wild;
• Endangered (EN): a taxon considered to be facing a very high risk of extinction in the wild;
• Critically Endangered (CR): a taxon considered to be facing an extremely high risk of extinction in the wild;
• Extinct in the Wild (EW): a taxon known to survive in cultuvation, captivity or as a neutralised population well outside the past range. A taxon is presumed EW when surveys in the wild have failed to record it;
• Extinct (EX): a taxon which surveys have failed to record.

/ˈkɑːbəneɪt//ˈhɑːdnəs/

Carbonate hardness is the measure of the alkalinity of water, determined by the presence of carbonates of calcium. Carbonate hardness is related to the ability of water to maintain a stable environment and a stable pH.

/liːf ˈlɪtər zoʊn/

Leaf Litter Zone refers to an aquatic biotope zone dominated by submerged leaf litter, including fallen leaves, twigs, seeds, and other decomposing plant material accumulating on the bottom of water bodies.

This zone is typical of tropical and subtropical freshwater ecosystems, especially in rainforest environments such as the Amazon Basin, Central Africa, and Southeast Asia, where riparian vegetation continuously supplies organic matter to the aquatic system.

From an ecological perspective, the Leaf Litter Zone plays a fundamental role:

• the decomposition of leaves releases tannins and humic acids, often resulting in darkly stained (blackwater) conditions and lower pH values;
• the leaf litter creates highly structured microhabitats, essential for invertebrates, microorganisms, fry, and small fish;
• it provides shelter, feeding grounds, and spawning sites for numerous aquatic species.

Typical environmental conditions include:

• slow-moving to stagnant waters, often shallow;
• reduced light penetration, due to dense forest canopy cover;
• low mineral content and reduced conductivity;
• variable, often lower dissolved oxygen levels compared to flowing-water zones.

In biotope aquarium keeping, the Leaf Litter Zone is recreated using natural botanical materials (e.g. Terminalia catappa, Quercus, Fagus, Magnolia leaves), branches, and driftwood, aiming to reproduce natural water chemistry, habitat complexity, and authentic species behaviour.

/ˈlɛvəl//ɒv//kəmˈplɛksɪti/

With regard to the forms in the sections BAM, FISH, and PLANT, it refers to the level of complexity to decorate the biotope tank, find the species and décor material in the general aquarium shops and manage a species in a biotope correct aquarium. Ratings are: easy, medium or difficult.

/laɪt ɪnˈtɛnsɪti/

Light intensity is the amount of light available in an aquatic habitat, measured in lux or PAR (Photosynthetically Active Radiation).

Detailed Description:

• Affects photosynthesis, plant growth, fish behavior, and coloration.
• Varies with depth, turbidity, canopy cover, and water color.

Ecological / Aquaristic Relevance:

• Critical for plant growth, diurnal activity patterns, and breeding cycles.
• Adjusting light intensity in tanks replicates natural habitats.

Example:

• Shaded blackwater streams: low light, favors leaf litter plants.
• Shallow tropical rivers: high light, supporting macrophytes and colorful fish.

/ˈlɪtərəl zoʊn/

The littoral zone is the shallow part of a water body near the shore, extending from the high-water mark to where light penetrates to the bottom.

Detailed Description:

• Often contains macrophytes, emergent vegetation, and benthic organisms.
• Supports high species diversity due to light, shelter, and nutrient availability.

Ecological / Aquaristic Relevance:

• Critical for spawning, feeding, and hiding of fish and invertebrates.
• Aquaria replicating littoral zones include shallow shelves, plants, and substrates.

Example:

• Shallow lake margins with Echinodorus and Lemna support juvenile characins.
• Rocky littoral zones in rivers host gobies and blennies.

/ˈlɒtɪk/ (UK), /ˈloʊtɪk/ (US)

Lotic describes freshwater environments characterised by flowing water, such as rivers, streams, creeks, and fast-flowing channels. The term is used in limnology and aquatic ecology to distinguish running-water systems from lentic (standing-water) environments.

Lotic habitats are defined by the presence of current velocity, which strongly influences physical structure, oxygen availability, sediment composition, and biological communities. Flow regimes may range from slow and laminar to fast and turbulent, creating a mosaic of microhabitats within the same watercourse.

Key characteristics of lotic systems include:

• continuous water movement, shaping substrate and channel morphology;
• generally higher dissolved oxygen levels, especially in riffles and rapids;
• substrates sorted by current strength, from fine sediments in slow zones to gravel, cobble, or bedrock in fast-flowing areas;
• organisms often show morphological and behavioural adaptations to resist or exploit current (e.g. streamlined bodies, adhesion behaviours).

In natural biotopes, lotic environments support diverse fish, invertebrate, and plant communities adapted to specific flow conditions and seasonal fluctuations.

In biotope aquarium design, the term lotic is used to define aquaria that replicate running-water habitats, with directional flow, oxygen-rich conditions, and substrates arranged according to current dynamics, in order to reproduce natural behaviour and ecological relationships of lotic species.

/ˈmæŋɡroʊv ˈfɒrɪst/ (UK), /ˈmæŋɡroʊv ˈfɔːrɪst/ (US)

A Mangrove Forest is a coastal intertidal ecosystem dominated by salt-tolerant woody plants (mangroves) that grow along tropical and subtropical shorelines, estuaries, river mouths, and sheltered coastal lagoons.

Mangrove forests occur at the interface between marine, brackish, and freshwater systems, and are strongly influenced by tidal cycles, variable salinity, and fine sediment deposition. The complex root structures (prop roots, pneumatophores) stabilise sediments and create highly structured habitats.

From an ecological perspective, mangrove forests are of exceptional importance:

• they function as nursery grounds for fish, crustaceans, and other aquatic organisms;
• they provide shelter and feeding areas for juvenile and adult species;
• they trap organic matter and sediments, enhancing nutrient cycling and water quality;
• they protect coastlines from erosion and wave action.

Typical environmental conditions include:

• fluctuating salinity, ranging from nearly freshwater to fully marine;
• soft, muddy substrates rich in organic material;
• warm water temperatures and often low to moderate dissolved oxygen;
• variable water levels driven by tides.

In the context of biotope aquarium keeping, mangrove forests are represented by brackish or estuarine aquaria using mangrove roots or analogues, fine sediments, and tidal or flow simulation, with the aim of reproducing natural habitat complexity, salinity gradients, and species interactions characteristic of mangrove ecosystems.

/məˈriːn//fɪʃ/ /əˈkweəriəm/

This is a salt water tank that houses colourful marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only, fish only with live rock, and reef aquaria.

/məˈriːn//fɪʃ//ˈbʌɪə(ʊ)təʊp/

Physical characteristics
At a given scale, a habitat encompasses a spatial domain, homogeneous in relation to environmental parameters. The environment’s physical and chemical characteristics are taken to encompass the substratum (rock or sediment) and the particular conditions, which are characteristic of the local environment. For the marine environment such conditions include wave exposure, salinity and tidal currents. Such conditions vary within a range, which is characteristic of the habitat. This means that a habitat is limited in space. The biotope integrates the environmental factors which structure the habitat. With regard to physical parameters, the biotope results from a balance between hydrodynamic parameters, physico-chemical parameters such as salinity and continental inputs (including pollutants and nutrients), the local geomorphology creating sheltered or exposed habitats, regional sedimentary characteristics and regional lithology conditioning the type of deposit or the type of substratum. The habitat is indicated by a limited set of words resuming the local conditions, i.e. muddy sand or rock platform. Such expressions integrate the various parameters which play a role in the habitat of a particular population.

Biological features
The term ‘habitat’ is more widely (and abusively) used to also include living organisms. Within space, species interact and constitute communities. From a biological point of view, the bio-facies or biotope results from a balance between the regional living environment and the local conditions. The presence of a species will be dependant on access to the ecosystem considered and to other biological requirements, i.e. the recruitment of young stages, trophic conditions.

/məˈriːn//fɪʃ/

Marine, or saltwater fish are all those fish species that live in the ocean, where they either live alone or form schools. Different marine fish species live in different marine habitats, that can largely vary in terms of salinity and alkalinity levels, temperature, and pH values.

Marine fish species are commonly kept in home aquaria and they are constantly threatened by the fish industry.

/ˈmeɪ.tɪŋ taɪp/

Mating type describes the reproductive strategy a fish species uses to pair or group for spawning, including whether they form temporary or long-term pairs, mate in groups, or have other complex mating behaviors.

Mating Types in Fish:

/ˈmaɪkroʊˌhæbɪtæt/

A microhabitat is a small, distinct physical and ecological unit within a larger habitat, characterised by specific environmental conditions that differ from the surrounding area.

In aquatic ecosystems, microhabitats are created by variations in substrate type, water flow, depth, light availability, temperature, and chemical conditions, as well as by structural elements such as rocks, wood, leaf litter, roots, and aquatic vegetation. Examples include leaf litter accumulations, root tangles, shaded margins, submerged logs, riffles, and pools.

Microhabitats play a critical ecological role:

• they support high biodiversity by allowing species with different requirements to coexist within the same system;
• they provide specialised niches for feeding, shelter, and reproduction;
• they are essential for juvenile stages, offering protection from predators and strong currents;
• they drive behavioural and spatial segregation among species.

In natural biotopes, the distribution and stability of microhabitats are influenced by seasonal changes, hydrology, and disturbance events.

In biotope aquarium design, the deliberate creation of multiple microhabitats within a single aquarium is fundamental to accurately reproducing natural ecological complexity, encouraging authentic behaviour, and improving long-term species welfare.

/maɪˈɡreɪʃən ruːt/

A migration route is a regularly used pathway or corridor followed by organisms during seasonal or life-cycle movements between different habitats, such as feeding, breeding, nursery, or refuge areas.

In aquatic ecosystems, migration routes often connect rivers, floodplains, lakes, estuaries, and coastal waters, and may involve movements over short or long distances. These routes are typically shaped by hydrological cycles, including rainfall patterns, flooding events, water temperature, and flow dynamics.

Migration routes are ecologically critical because they:

• enable access to essential habitats required at different life stages;
• support reproductive success and population connectivity;
• facilitate genetic exchange between sub-populations;
• allow species to respond to seasonal environmental changes.

Disruption of migration routes – through dams, channel modification, pollution, or habitat loss—can severely impact migratory species and entire aquatic communities.

In biotope aquarium interpretation, the concept of migration routes is used to explain natural life-cycle strategies and habitat connectivity, even though such large-scale movements cannot be fully replicated in captivity. Understanding migration routes helps guide species selection, educational displays, and conservation-oriented biotope design.

/ˈmɒnɪtərɪŋ/

Collection and comparison of information to determine type, extent and cause of change.

/ˌmɒnə(ʊ)ˈmɔːfɪk/

In biology,

• (of a species or population) showing little or no variation in morphology or phenotype.
• (of an animal species) having sexes that are similar in size and appearance.

/ˌmɒnəʊˈtɪpɪk/

In biology, a genus or species with only one type of representative. A monotypic taxon is a taxonomic group that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or infraspecific taxa. In the case of genera, the term “unispecific” or “monospecific” is preferred.

/ˈmɔːrfətaɪp/

A morphotype is a distinct form or variant within a species or population, defined by consistent morphological characteristics such as body shape, size, coloration, patterning, or structural features.

Morphotypes may arise as a result of genetic variation, environmental influences, or phenotypic plasticity, and can occur within the same geographic area or across different habitats. In aquatic organisms, morphotypes are often associated with specific microhabitats, ecological niches, or environmental conditions such as flow regime, substrate type, depth, or predation pressure.

Key features of morphotypes include:

• they belong to the same species, despite visible differences;
• they do not represent formal taxonomic units;
• differences are typically stable and recognisable, but may be reversible or variable under changing conditions.

In natural ecosystems, morphotypes can reflect adaptive strategies that improve survival and resource use within heterogeneous environments.

In biotope aquarium and scientific documentation, the term morphotype is used to describe locally adapted forms or visually distinct populations without assigning taxonomic rank, supporting accurate habitat representation while avoiding misidentification as separate species.

/ˈnaɪtreɪt ˈlɛvəl/

Nitrate level refers to the concentration of nitrate (NO₃⁻) dissolved in water, commonly expressed in milligrams per litre (mg/L). Nitrate is the final product of the nitrogen cycle in aquatic ecosystems, formed through the biological oxidation of ammonia and nitrite by nitrifying bacteria.

In natural freshwater and estuarine environments, nitrate levels vary depending on organic input, biological uptake, hydrology, and water exchange. Low to moderate nitrate concentrations are normal and support plant and microbial growth, while elevated levels may indicate nutrient enrichment or pollution.

Ecological significance of nitrate levels includes:

• influence on primary productivity and algal growth;
• interaction with oxygen dynamics, particularly in nutrient-rich systems;
• potential impacts on fish health and invertebrate communities at high concentrations.

In biotope aquarium keeping, controlling nitrate levels is essential for maintaining stable water quality and reproducing natural conditions. Nitrate is managed through regular water changes, biological filtration, plant uptake, and controlled feeding, with target levels adjusted according to the specific biotope and species requirements.

/ˌnaɪtrɪfɪˈkeɪʃən/

Nitrification is a biological oxidation process within the nitrogen cycle in which ammonia (NH₃/NH₄⁺) is converted first into nitrite (NO₂⁻) and then into nitrate (NO₃⁻) by specialised aerobic bacteria.

This process occurs in oxygen-rich aquatic environments and is primarily driven by two groups of microorganisms:

• ammonia-oxidising bacteria (and archaea), which convert ammonia into nitrite;
• nitrite-oxidising bacteria, which convert nitrite into nitrate.

Nitrification plays a crucial ecological role by:

• reducing the toxicity of ammonia and nitrite;
• making nitrogen available in a more stable form;
• linking organic waste decomposition to nutrient cycling.

In natural biotopes, the efficiency of nitrification depends on oxygen availability, temperature, pH, and surface area for bacterial colonisation.

In biotope aquarium systems, nitrification is fundamental to biological filtration and long-term stability. It takes place on filter media, substrates, and hard surfaces, and must be fully established before sensitive species are introduced.

/ˈnaɪtrədʒən ˈsaɪkəl/

The nitrogen cycle is a biogeochemical process through which nitrogen is transformed and circulated between organic and inorganic forms within aquatic ecosystems.

In freshwater and estuarine environments, the nitrogen cycle involves several key stages:

• Ammonification, where organic nitrogen from waste, dead organisms, and plant material is converted into ammonia;
• Nitrification, an aerobic process converting ammonia into nitrite and then nitrate;
• Assimilation, where plants, algae, and microorganisms take up ammonia or nitrate for growth;
• Denitrification, an anaerobic process in which nitrate is reduced to gaseous nitrogen, returning it to the atmosphere.

The balance of these processes regulates nutrient availability, water quality, and ecosystem stability. Disruptions can lead to ammonia or nitrite toxicity, excessive nitrate accumulation, or eutrophication.

In biotope aquarium keeping, understanding the nitrogen cycle is essential for:

• establishing effective biological filtration;
• maintaining safe and stable water chemistry;
• reproducing natural nutrient dynamics found in specific biotopes;
• ensuring the health and long-term survival of aquatic organisms.

/nɒkˈtɜːrnəl ækˈtɪvɪti/

Nocturnal activity in fish refers to a behavioural pattern in which individuals are primarily active during nighttime hours and remain inactive, hidden, or less visible during the day.

Nocturnal fish are typically adapted to low-light or dark environments, such as shaded forest streams, deep waters, turbid systems, caves, or leaf litter zones. Common adaptations include enhanced sensory systems, such as improved lateral line sensitivity, chemoreception, or reduced reliance on vision.

Ecological significance of nocturnal activity includes:

• reduced predation risk by avoiding visually oriented predators;
• access to food resources that are more available at night;
• temporal niche partitioning, allowing coexistence with diurnal species.

In natural biotopes, nocturnal activity patterns are influenced by light cycles, habitat structure, water turbidity, and moon phase.

In biotope aquarium keeping, recognising nocturnal activity is essential for:

• providing appropriate shelter and shaded microhabitats;
• designing lighting regimes that respect natural behaviour;
• understanding feeding behaviour and visibility of species during daylight hours.

/ˌnɪmfiˈeɪsiːaɪ/

Nymphaeaceae is a family of aquatic flowering plants commonly known as the water lily family, consisting of rooted, perennial plants adapted to still or slow-moving freshwater habitats.

Members of the Nymphaeaceae typically grow in lentic environments such as ponds, lakes, floodplains, oxbows, and slow river margins. They are characterised by large floating leaves, long flexible petioles, and showy flowers that emerge at the water surface.

Ecological roles of Nymphaeaceae include:

• providing shade and thermal buffering to the water below;
• creating shelter and spawning sites for fish and invertebrates;
• reducing light penetration, influencing algal growth and underwater vegetation;
• contributing organic matter to detrital food webs when leaves decay.

Species within this family are distributed worldwide in tropical, subtropical, and temperate regions, with notable genera including Nymphaea, Victoria, and Euryale.

In biotope aquarium and habitat interpretation, Nymphaeaceae are used to represent natural still-water or floodplain systems, helping recreate authentic surface structure, light conditions, and ecological interactions typical of water lily–dominated habitats.

/ˈämnəˌvôr/

Omnivore fish species possess a versatile diet, consuming both plants and smaller aquatic animals. This adaptability allows them to thrive in various habitats, contributing to their diverse presence across the world’s waters.

An omnivore will eat a variety of meat and vegetable matter. Although omnivores can and will eat vegetable matter, they cannot digest some types of grains and plants. Their teeth and digestive tract possess some of the traits of both the carnivore and the herbivore.

Omnivores are the easiest of all fish to feed, as they eat flake foods as well as live foods, and everything in between. For that reason, omnivores are an excellent choice for a community tank.

It’s important to feed your fish the proper diet, as their bodies are designed for certain types of food.

/ɒnˈtɒdʒəni/

In biology, the process of individual development from a single cell, an egg cell or a zygote, to an adult organism is known as ontogeny.

/ˌɔːnəˈmɛntl//fɪʃ/

An ornamental fish is a fish that is kept in home aquarium for aesthetic purposes. There are a lot of different fish species that are considered ornamental and that can be included in home aquaria; they encompass a wide variety of species, of many shapes, sizes, and colours.

Osmoregulation in fish is the physiological process by which fish maintain the balance of water and salts (ions) in their body to survive in different aquatic environments. Essentially, it’s how fish control their internal osmotic pressure relative to the surrounding water.

1. Why it’s important

• Fish live in water that can be freshwater (low ion concentration) or saltwater (high ion concentration).
• Osmoregulation prevents them from losing too much water in saltwater or taking in too much water in freshwater.
• It ensures that cells maintain the right concentration of ions like sodium (Na⁺), potassium (K⁺), and chloride (Cl⁻) for metabolism.

2. Mechanism in freshwater fish

• Freshwater is hypotonic (less salty) compared to the fish’s body fluids.
• Water tends to enter the fish by osmosis, which could swell cells.
• Fish adaptations:
  • Excrete large volumes of dilute urine to remove excess water.
  • Actively uptake ions (Na⁺, Cl⁻) through gills and kidney to maintain salt levels.

3. Mechanism in saltwater fish

• Saltwater is hypertonic (more salty) than the fish’s body fluids.
• Water tends to leave the fish by osmosis, causing dehydration.
• Fish adaptations:
  • Drink seawater to replace lost water.
  • Excrete excess salts through specialized chloride cells in gills and concentrated urine.

4. Special cases

• Euryhaline fish (like salmon) can survive in both freshwater and saltwater by switching osmoregulatory mechanisms.
• Osmoconformers (mostly marine invertebrates) match their internal osmotic pressure to the environment, unlike most fish.

5. Summary

Osmoregulation is critical for survival in different water types. Without it, fish would either dehydrate in saltwater or swell and burst in freshwater. It involves a combination of kidney function, gill ion transport, and behavioral adaptations.

/ˈɒksɪsˌɒl/

Oxisols (from French oxide, “oxide”) are very highly weathered soils that are found primarily in the intertropical regions of the world. These soils contain few weatherable minerals and are often rich in Fe and Al oxide minerals.

The main processes of soil formation of oxisols are weathering, humification and pedoturbation due to animals. These processes produce the characteristic soil profile. They are defined as soils containing at all depths no more than ten percent weatherable minerals, and low cation exchange capacity.

/ˌpærəˈmiːʃ(i)əm/

Paramecium or Paramoecium is a genus of unicellular ciliated protozoa characterised by the presence of thousands of cilia covering their body. Paramecium are found in freshwater, marine and brackish water. They are also found attached to the surface. Reproduction is primarily through asexual means (binary fission).

In the aquaristics Paramoecium and rotifers are known under the collective name Infusoria which stands for microscopic organisms that dwell in waterbodies, feeding on detrietus and smaller single celled organisms.

/pəˈrɛniəl//ˈplɑːnt/

A plant whose life cycle extends for more than two years (e.g. Cyperus).  Some perennials, such as grasses and herbs, have above-ground parts, which die off in unfavorable seasons leaving an underground structure, such as a bulb or rhizome, to produce new growth when the season is favourable.

/pəˈrɛniəl//ˈrIvUH/

Perennial rivers have an uninterrupted flow of water throughout the year, regardless of the season, although some perennial rivers could stop flowing during severe drought. Perennial rivers drain a huge area forming the basin of the river, such as instance the Amazon River, which covers an area of 7.500.000 km² and is the largest basin in the world. The Congo River in Africa drains an area of 4.014.500 km², making it the second largest river basin in the world.

Scale indicative of the acidity or basicity of a substance, that is influenced by minerals and dissolved materials. A substance is acid when its pH ranks between 0 and 5,5 and basic, or alkaline, when its pH is between 7,5 and 14. When the pH is between 5,5 and 7,5, a substance is considered neutral.

/ˈfʌɪtəʊˈplæŋ(k)t(ə)n/

Derived from the Greek words phyto (plant) and plankton (made to wander or drift), phytoplankton are microscopic organisms that live in watery environments, both salty and fresh.

Some phytoplankton are bacteria, some are protists, and most are single-celled plants. Among the common kinds are cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores.

Like land plants, phytoplankton have chlorophyll to capture sunlight, and they use photosynthesis to turn it into chemical energy. They consume carbon dioxide, and release oxygen. All phytoplankton photosynthesize, but some get additional energy by consuming other organisms.

Phytoplankton growth depends on the availability of carbon dioxide, sunlight, and nutrients. Phytoplankton, like land plants, require nutrients such as nitrate, phosphate, silicate, and calcium at various levels depending on the species. Some phytoplankton can fix nitrogen and can grow in areas where nitrate concentrations are low. They also require trace amounts of iron which limits phytoplankton growth in large areas of the ocean because iron concentrations are very low. Other factors influence phytoplankton growth rates, including water temperature and salinity, water depth, wind, and what kinds of predators are grazing on them.

/ˈfʌɪtəʊrɪˌmiːdɪˈeɪʃ(ə)n/

Phytoremediation is a bioremediation process that uses various types of plants to remove, transfer, stabilize, and/or destroy contaminants in the soil and groundwater.

Worldwide population is generating an enormous amount of waste discharged into waterways. Waste dominated one of them is domestic waste. Domestic waste is divided into two categories: first, domestic waste water from the washing water such as soaps, detergents, oils and pesticides; The second is the liquid waste from the latrines such as soap, shampoo, feces and urine. This wastewater as a potential environmental pollutant if not managed properly. The result of this waste water enters the body when water will affect the condition of the water body. The more densely populated, the more waste that must be controlled.

Heavy metal accumulation in soil has been rapidly increased due to various natural processes and anthropogenic (industrial) activities. As heavy metals are non-biodegradable, they persist in the environment, have potential to enter the food chain through crop plants, and eventually may accumulate in the human body through biomagnification. Owing to their toxic nature, heavy metal contamination has posed a serious threat to human health and the ecosystem. Therefore, remediation of land contamination is of paramount importance. Phytoremediation is an eco-friendly approach that could be a successful mitigation measure to revegetate heavy metal-polluted soil in a cost-effective way.

There are several different types of phytoremediation mechanisms. These are:

1. Rhizosphere biodegradation. In this process, the plant releases natural substances through its roots, supplying nutrients to microorganisms in the soil. The microorganisms enhance biological degradation.
2. Phyto-stabilization. In this process, chemical compounds produced by the plant immobilize contaminants, rather than degrade them.
3. Phyto-accumulation (also called phyto-extraction). In this process, plant roots sorb the contaminants along with other nutrients and water. The contaminant mass is not destroyed but ends up in the plant shoots and leaves. This method is used primarily for wastes containing metals. At one demonstration site, water-soluble metals are taken up by plant species selected for their ability to take up large quantities of lead (Pb). The metals are stored in the plantÍs aerial shoots, which are harvested and either smelted for potential metal recycling/recovery or are disposed of as a hazardous waste. As a general rule, readily bioavailable metals for plant uptake include cadmium, nickel, zinc, arsenic, selenium, and copper. Moderately bioavailable metals are cobalt, manganese, and iron. Lead, chromium, and uranium are not very bioavailable. Lead can be made much more bioavailable by the addition of chelating agents to soils. Similarly, the availability of uranium and radio-cesium 137 can be enhanced using citric acid and ammonium nitrate, respectively.
4. Hydroponic Systems for Treating Water Streams (Rhizofiltration). Rhizofiltration is similar to phyto-accumulation, but the plants used for cleanup are raised in greenhouses with their roots in water. This system can be used for ex-situ groundwater treatment. That is, groundwater is pumped to the surface to irrigate these plants. Typically hydroponic systems utilize an artificial soil medium, such as sand mixed with perlite or vermiculite. As the roots become saturated with contaminants, they are harvested and disposed of.
5. Phyto-volatilization. In this process, plants take up water containing organic contaminants and release the contaminants into the air through their leaves.
6. Phyto-degradation. In this process, plants actually metabolize and destroy contaminants within plant tissues.
7. Hydraulic Control. In this process, trees indirectly remediate by controlling groundwater movement. Trees act as natural pumps when their roots reach down towards the water table and establish a dense root mass that takes up large quantities of water.

/plænt fɔːrm/

Plant form describes the general growth habit of an aquatic plant in relation to the water surface — whether it grows submerged, floating, or above water. It reflects how plants adapt to aquatic environments and determines their ecological role in a biotope.

/plænt ɡroʊθ reɪt/

Plant growth rate refers to the speed at which an aquatic plant increases in size, spreads, or develops new leaves or shoots. Growth rate is influenced by environmental factors such as light intensity, nutrient availability, water chemistry, temperature, and CO₂ levels. Understanding a plant’s growth rate helps aquarists plan aquascaping, maintenance schedules, and compatibility with other species in a biotope aquarium.

Plant Growth Rate

/plant’lit/

Plantlets are young or small plants that can grow or be produced on the margins of the plant itself as a form of asexual reproduction.

/plænt laɪt dɪˈmænd/

Plant light demand refers to the amount and intensity of light that an aquatic plant requires to grow, maintain coloration, and complete its life cycle. Light is a critical factor for photosynthesis, which provides the energy needed for plant development, leaf formation, flowering, and reproduction.

Different species have evolved to thrive under varying light conditions, ranging from shaded, low-light environments (e.g., under floating plants or in dense forests) to brightly illuminated streams and shallow waters. Aquarists must consider light spectrum, intensity, duration, and distribution when designing aquascapes or biotope aquariums, because insufficient or excessive light can lead to stunted growth, poor coloration, algae overgrowth, or plant decay.

Light demand also interacts with nutrient availability, CO₂ levels, and water chemistry, meaning a plant’s light requirement cannot be considered in isolation. Properly assessing and providing the right light conditions is essential for creating a balanced, healthy, and visually appealing aquarium ecosystem.

Plant Light Demand

/plænt taɪp/

Plant type (or plant form) refers to the morphological growth habit and structural characteristics of an aquatic plant or algae. It describes how a plant grows, spreads, and organizes its leaves or stems, which affects its ecological role, placement in the aquarium, and care requirements. Plant type classification helps aquarists, researchers, and hobbyists understand the growth patterns, propagation methods, and spatial use of plants in natural and artificial freshwater ecosystems.

Plant types include true vascular plants and macroalgae, as both form functional structures in aquariums or biotopes. The classification considers features such as:

• Growth habit (upright stems, horizontal runners, mats, rosettes)
• Propagation method (rhizomes, stolons, bulbs, fragmentation)
• Leaf arrangement (whorled, rosette, carpet-like)
• Ecological role (oxygenation, shelter, substrate coverage)

Plant Types

/ˈrio/ /ˈnapoʔ/

The Napo Basin covers about 101.0000km², or 1.5% of the Amazon, and is the smallest of the Amazon tributaries, which cover at least 100.000km². Of the Amazon’s major tributaries, the Napo is longer only than the Trombetas at 885km.

About 60% of the Napo Basin is in Ecuador; the remaining 40% is in Peru. The Napo Basin makes up the majority of the Amazon River drainage area in Ecuador. The Napo Basin, located in Peru, is entirely in the Loreto Region. The Ecuadorian portion of the valley is divided among four provinces, more than half of which are in the larger Napo Province.

The Napo River’s headwaters originate 100–200km from Quito, the capital of Ecuador, in the high Andes. The headwaters of the Napo River in the Andes above about 400m are clear except during periods of heavy rainfall. In the lowlands, the Napo River is muddy and heavily meandering, with a large floodplain. The Curaray, a blackwater river with sections in Ecuador and Peru, is the only major tributary of the Napo. There are also numerous smaller blackwater tributaries in the Napo basin from the foothills to its mouth.

Annual rainfall in the Napo basin varies from about 2.500 to 5.000mm. Most rainfall occurs on the slopes of the Andes. The average annual fluctuation of the river level in the lower Napo in Peru is about 8.5m, similar to that of the Amazonas near Iquitos. The floodplains along the Napo River are flooded from about December to May each year.

/rʌɪˈpɛːrɪən/ /zəʊn/

The area between land and a watercourse, characterized by the presence of many aquatic plants and other vegetation that can grow to create ana actual forest on the banks of a river. The riparian zone is important for the wellness and the protection of the aquatic environment.

/ˈrɪvəbɛd/

A riverbed is the bed or the channel in which a river flows and that is shaped by the flowing water. A riverbed can be more or less wide, from a few feet to a thousand metres. Nevertheless, from time to time a riverbed might not contain flowing water or be dry all the same. This particularly happens in regions of the world where dry and rain season alternate. Furthermore, riverbeds can consists of different materials, such as rock, sand, clay, silt, or other unconsolidated materials resulting from earlier deposition.

/ˈrɪvə//ˈkatʃm(ə)nt/

Area of land around a river or another water body that is collected in that area because of the conformation of the landscape. All the water that is collected in the same catchment area eventually flows together in the same water body.

/raɪzəʊm/

A rhizome is a horizontal underground plant stem, which is able to produce the shoot and root systems of a new plant. These stems allow a parent plant to produce offrispring through asexual reproduction, that is, propagation, and to survive in adverse condition. The rhizomes perform several functions that help the growth of the plant, such as storing food and save nutrients (proteins, carbohydrates, minerals).

/ˈsɛmi/-/ˈærɪd/

It refers to climates or regions which lack sufficient rainfall for regular crop production.  Usually defined as a climate with annual rainfall greater than 250 mm but less than 375 mm.

/ˈsɔɪl//ɪˈrəʊʒ^ən/

The detachment and transportation of soil and its deposition at another site by wind, water or gravitational effects.

Natural erosion: erosion occurring under natural environmental conditions, undisturbed by humans.

Accelerated erosion: erosion which is attributable to the influence of human activities.  See also scald, hummockingand pedestalling.

Water erosion: an erosion process in which soil is detached and transported from the land by the action of rainfall,  runoff and seepage.  Types of water erosion include:

• Splash erosion: the spattering of soil particles caused by the impact of raindrops on the soil; an important component of sheet erosion.
• Sheet erosion: the removal of a fairly uniform layer of soil from the land surface by wind and raindrop splash and /or runoff. No rills are formed.
• Rill erosion: the removal of runoff from the land surface whereby numerous small channels are formed.  Rills are defined as small channels up to 30 cm deep.
• Gully erosion: the removal of soil by water whereby large incised channels (> 30 cm deep) are formed.  The severity of gully erosion may be recorded as minor, moderate, severe or very severe.  Gully erosion processes may include the removal of soil from the land surface by concentrated runoff or the dispersion of unstable subsoils.
• Stream bank erosion: the removal of soil from stream banks by the direct action of steam flow and/or wind /wave action. Typically occurs during periods of high flow.
• Wind erosion: the removal and transportation of soil by wind. (See sheet erosion)

/ˈsʌbˌspiːʃiːz ɪn ˈbɒtəni/

Subspecies (in Botany)
A formally recognized taxonomic rank under the International Code of Nomenclature for algae, fungi, and plants (ICN). In botanical taxonomy, subspecies is a commonly used and widely accepted category.

A subspecies represents a geographically or ecologically distinct population within a species that shows consistent morphological differences, but not enough divergence to warrant classification as a separate species. Unlike in zoology—where the use of subspecies has declined—the concept remains active and practical in plant taxonomy.

Key Characteristics:

• Subspecies can often interbreed with other subspecies of the same species.
• They are clearly distinguishable, often by habitat, range, or physical traits.
• The rank of subspecies is higher than variety (var.) and form (f.), which represent increasingly finer levels of variation.

Example:

1. Potamogeton natans subsp. spathulatus
   Common name: Broad-leaved pondweed
   Notes: A subspecies found in specific freshwater habitats; differs in leaf shape and habitat preference.
2. Ranunculus aquatilis subsp. diffusus
   Common name: Water crowfoot
   Notes: A submerged aquatic plant; subspecies vary by morphology and habitat conditions (e.g., still vs. flowing water).
3. Sparganium erectum subsp. microcarpum
   Common name: Branched bur-reed
   Notes: Grows in slow-moving or still water; subspecies differ in fruit size and leaf structure.
4. Typha domingensis subsp. angustifolia
   Common name: Narrow-leaved cattail
   Notes: Some taxonomic treatments recognize this as a subspecies rather than a separate species.
5. Lemna gibba subsp. minor (in some older classifications)
   Common name: Gibbous duckweed
   Notes: Though now often treated as distinct species, some sources historically list them as subspecies.
6. Alisma plantago-aquatica subsp. orientale
   Common name: Water plantain
   Notes: Found in Asia; differs slightly from the European subspecies in leaf and floral characteristics.

Subspecies are commonly used in regional floras, phylogenetic studies, and conservation planning, especially in plant groups with wide distribution and high ecological plasticity.

/ˈsʌbˌspiːʃiːz ɪn ˌɪkθiˈɒlədʒi/

Subspecies (in Ichthyology)
A formally recognized taxonomic rank under the rules of the International Code of Zoological Nomenclature (ICZN). While the term subspecies is still valid in ichthyology, its use has become increasingly rare and cautious in modern taxonomy.

Historically, subspecies were used to classify geographically or morphologically distinct populations within a species. However, advances in genetic and molecular research have led to a trend toward either elevating such populations to full species status or treating them as intraspecific variation (e.g., ecotypes or morphs) rather than formal subspecies.

In ichthyology today, the concept of subspecies is generally applied only when:

• Populations show consistent, diagnosable differences but do not warrant species-level separation.
• There is geographic isolation (e.g., island or landlocked populations) with limited gene flow.
• Historical literature or conservation frameworks require the designation.

Example:
The forms Salmo trutta fario (stream-dwelling) and Salmo trutta lacustris (lake-dwelling) were once classified as subspecies of the brown trout. Today, they are often considered ecological forms rather than formal subspecies.

For current usage, it is advisable to consult authoritative taxonomic databases such as FishBase, WoRMS, or Eschmeyer’s Catalog of Fishes, as subspecies designations are often revised or deprecated.

/ˈsʌbstreɪt//ɪn//əˈkwɛːrɪəm/

In the aquarium, the substrate corresponds to the materials used in the tank that should replicate the natural substrate and natural conditions for the species.

/ˈsʌbstreɪt//ɪn//ˈneɪtʃə/

The surface on which an organism lives. Regarding rivers, the substrate corresponds to its bottom, its constituents and sediments. The substrate can affect the biodiversity of a watercourse.

/ˈstægnənt/

With regard to water, it refers to the fact that it is motionless and still. Stagnant water can be confined, standing, experiencing a low flow or usage.

Because of its poor quality or shallow depth, stagnant water is unusable.

/sɪmˈpætrɪk ˈspiːʃiːz/

Sympatric species are different species that occur within the same geographic area and share at least part of their natural distribution, allowing them to encounter one another regularly in the wild.

In aquatic ecosystems, sympatric species often coexist within the same river system, lake, or wetland, but may occupy different ecological niches or microhabitats. This spatial, behavioural, or dietary separation helps reduce direct competition and enables stable coexistence.

Key aspects of sympatric species include:

• overlapping geographic ranges without physical barriers;
• coexistence driven by niche differentiation rather than isolation;
• potential interactions such as competition, predation, or mutual tolerance;
• in some cases, the presence of reproductive isolation mechanisms preventing hybridisation.

Sympatry contrasts with allopatry, where species are geographically separated, and parapatry, where ranges are adjacent with limited overlap.

In biotope aquarium keeping, selecting sympatric species from the same natural habitat supports:

• higher ecological authenticity;
• compatible environmental requirements;
• more natural behavioural interactions and reduced stress.

/ˈtɛmpərəl niːʃ/

A temporal niche refers to the specific time‑based pattern of activity or ecological function that a species exhibits within its environment. It describes when a species is most active or plays its ecological role — for example, day vs. night activity, seasonal breeding periods, or timing of feeding.

Explanation:
In natural habitats, organisms partition not only physical space but also time to reduce competition and exploit resources efficiently. Two species may occupy the same physical habitat but be active at different times (e.g., diurnal vs. nocturnal), allowing them to coexist without direct conflict.

In biotope aquariums, considering temporal niches helps aquarists replicate natural rhythms – such as lighting cycles, feeding schedules, and breeding periods – that align with the natural daily and seasonal patterns of the biotope being recreated.

In Practice (Biotope Aquariums):

• Designing light schedules that mimic dawn, daylight, dusk, and night periods.
• Timing feedings to reflect natural foraging behavior (e.g., nocturnal grazers fed in low light).
• Recognizing seasonal cues like temperature shifts and photoperiod changes for breeding.

Why It Matters:
Respecting temporal niches in biotope aquariums supports:

• Healthy behavior expression
• Reduced stress and competition
• More natural ecological interactions
• Increased likelihood of successful spawning and life cycle completion

/ˈtjuːbəkl/

Tubercles are skin nodules made of keratin, the same materials as hair, hooves, and fingernails. They are present on species representing at least 15 families of fishes, including even pet goldfish. In many species, tubercles are found only on males during the breeding season and are shed shortly there after. They are often called breeding tubercles for that reason. The main functions for tubercles include species recognition, fighting and defense of spawning territory or nests, and stimulation of breeding females.

/ˈwɔːtə//ˈbɒdi//pɑːt/

It refers to a more specific part of the interested water body, which is thus further divided in upper, medium, and lower body part.

/ˈwɔːtə//ˈkɛmɪstri/

With regard to the different sections of the BIOTOPE AQUARIUM Project, the category “Water Chemistry” groups all the information about the condition of water in the given biotope or in the Biotope Aquarium Model.

Under “Water Chemistry” are listed some information and the chemical parameters of the described watercourse. It lists the water type, water colour, water transparency, the concentration of sediments, water temperature, water flow/current, pH, conductivity, GH, KH, and dissolved oxygen.

/ˈwɔːtə//ˈkʌlə/

Colour is one of the organolectic properties of water. Its colour varies with its physical, chemical and bacteriological conditions. Colour can distinguish water in:

• Clear water: typical of water courses with a good flow. It appears clear and of a greenish colour. The pH is usually neutral or slightly acidic, the conductivity and the presence of dissolved materials is low,
• Black water: typical of water courses with a slow or no flow. It appears of a dark colour because of the tannins resulting from the decay of the vegetation. The pH is usually acidic and the conductivity low,
• White water: typical of water bodies that contain high levels of suspended sediments. The pH is usually neutral and the conductivity high,
• Mixed water: typical of water bodies that go through different environments, so that the water changes properties in the different parts of its course.

/əˈbʌv/ /ˈwɔːtəfɔːl/

A waterfall is an area where water flows over a vertical drop or a series of steep drops in the course of a stream or river.

A waterfall is a part of the river or other water bodies and it is caused by the water’s steep fall over a rocky ledge into a plunge pool below. Waterfalls are also called cascades. The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls.

A waterfall acts as a natural barrier that many fish species cannot cross. That is the reason why the fish fauna above waterfall might be different from the fish fauna below the waterfall, especially if influenced by tides, like it often happens on the islands of Papua New Guinea. An exception to this is represented by a few fish species who can climb up the waterfall with special adhesive organs, like a few gobies or Balitoridae that uses its suctioning mouth and/or a sucker on its stomach to inch upward against the flow of water.

/ˈwɔːtə//fləʊ/ˈkʌrənt//tʌɪp/

Water bodies usually have currents, that can be distinguished in surface currents and deep-water currents. When talking about a river, its flow can be lower or higher and determines how and how much water flows. Current is determined by many different factors, among which winds, gravity, water volume, riverbed conformation, etc.

/ˈwɔːtə/ /trɑːnsˈparənsi/

Water transparency is linked to the presence of particles suspended in the water and to the amount of light and sun radiations that can penetrate it and at what depth. The more transparent the water, the deeply sunlight can penetrate, thus enabling plants and organisms on the bottom to survive.

/ˈwɔːtə//tʌɪp/

Water type refers to the general physical and chemical nature of natural waters, classified according to origin, salinity, and mineral content. Water is divided into four main types:

1. Meteoric water – derived directly from precipitation such as rain or snow.

2. Surface water – found on the Earth’s surface, further subdivided into:

   • Fresh water, with very low salinity (<0.5‰), occurring in rivers, lakes, and streams.

   • Brackish water, of intermediate salinity (0.5–30‰), typically in estuaries and mangrove zones.

   • Marine water, with high salinity (~35‰), forming seas and oceans.

3. Telluric water – groundwater that emerges from springs or aquifers, often rich in minerals.

Understanding water types is essential in aquatic ecology and biotope aquarium design, as each supports distinct plant and animal communities adapted to its conditions.

However, aquaristics focuses on three principal water types according to salinity:

1. Fresh water – with very low salinity (<0.5‰), typical of rivers, lakes, and streams.

2. Brackish water – of intermediate salinity (0.5–30‰), where fresh and marine waters mix, such as in estuaries or mangroves.

3. Marine (salt) water – high in salinity (around 35‰), forming seas and oceans.

This threefold division forms the basis for aquarium practice, as each water type determines the suitable flora, fauna, and biotope design.