bam Very demanding level

Igarapé do Daracua near Barcelos, Brazil

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Brazil, Amazonas, Barcelos

In this 106L aquarium, the small part of the water forms the Igarapé do Daracua, shallow blackwater habitat in the Middle Rio Negro, near Barcelos, Brazil. I have introduced my Cardinal Tetras (Paracheirodon axelrodi) which is a popular freshwater fish that is native to the Rio Negro basin and found in abundant in shoals in the Igarapé do Daracua.

The biotope project was designed to recreate the underwater landscape of the Igarapé do Daracua. For the floor, I have used extremely fine river basin sand and its roots and trunks exposed, this flooded forest tree, dying and fallen decaying leaves is what causes the large amount of organic debris to be present in their waters, turning them black and enhancing the Cardinal Tetras colours and iridescence. The fallen Bactris major palm leaf creating a backdrop just like in nature.

Since Cardinal Tetras are photophobic, dappled sunlight filtering from the leaves in the aquarium just like in Nature.

Submitted by
Protim Sarkar
Approved by
Roberto E. Reis, Pablo C. Lehmann and Flávio Lima
-0.5067783, -63.2144890
Geographical region
South America
Drainage Basin
Amazon River Basin
River catchment
Rio Negro
Water body type
Water body name
Igarapé do Daracua
Water body part
River mouth
Water body course
Lower course
Water body: tributary of
Tributary name
Rio Negro

Videos above and below water

Water Chemistry

Water information

Water type
Fresh water
Water color
Black water
Water transparency
Concentration of sediments
Water temperature
26 °C
Water flow/curent

Chemical parameters

4 mg/l
4 mg/l
Dissolved Oxygen
90 %

Aquarium information

Aquarium description

Set-up date
January, 2022
Aquarium decoration

Similar to my project, my 106-litre aquarium contains 10 kg of extremely fine beige river basin sand that was gathered from a nearby river. In my tank, I’ve utilised a lot of botanicals. I put a lot of dried magnolia leaves on the sand bed. Jacaranda, Gouri fruit, Sterculia, Swietenia mahagoni, and Tucanorum fruits are some additional botanicals, fruits, and pods that I have used.

All of this organic material releases a lot of tannin, naturally turning the water black, and also lowers the pH, maintaining it at around 4.0.

The rear part of the aquarium which I have used is white vinyl. Backdrop and front consists of fallen green leaves of Bactris major just like in nature. The centre of attraction is the driftwood collected from my locality making the environment more welcoming for the fish which are constantly swimming through the roots in the dappled light. There are little to no aquatic plants in my biotope.

Aquarium equipment

• Filtration-SOBO Hanging Aquarium Filter Pump 280L/H set to minimum flow with 250 grams of ceramic media and mechanical filtering blanket
• Lighting- Spotlight 3 Watt placed at an angle 25º (Warm Yellow Colour)

Fish care

The considerable amount of tannins contained in the water severely sullies the mechanical filtering element, hence routine maintenance includes a 20% top-up water change and monthly filter cleaning.

Every week, parameters are measured and, if necessary, modified. The replacement water from evaporation and top-ups receive the same attention and are already stored with some leaves so that it has physicochemical characteristics as near to the water of the aquarium as possible.

Once daily, the fish are fed, preferably with food designed for tetras and occasionally with live baby brine shrimps.


  • Paracheirodon axelrodi
Plant care

Major flora are absent from my biotope. I only change the green Bactris major leaves once a month if they start to deteriorate.

Water care

I interchange 20% of my water in partial exchanges every month, as was already described. In order to add some tannins and acidify it, the make-up water is treated with antichlorine and preserved with a few dried leaves.

I use a buffer to maintain a steady pH equilibrium. Since the aquarium is inside the house and the weather is cool during winter, I occasionally use a heater to maintain the temperature.


76 cm
45 cm
30 cm
106 L

Substrate in aquarium

Stone form
Submerged terrestrial vegetation

Comment by the expert

Roberto E. Reis: Fish and decoration selected properly, but one single species displayed, despite 13 species listed in BIN. The aquarium looks beautiful and balanced, but the only short video presented shows little. Description of tank and external resources well done.

Flávio Lima: The biotope reproduces well the aquatic habitat of a typical large dark-water stream as the Igarapé do Daracuá, but as it only includes its most famous inhabitant, the cardinal tetra, it felt short to be a a true biotope.

Pablo C. Lehmann: The biotope project recreates the underwater landscape of Igarapé do Daracua reliably.