bam Demanding level

Urubaxi River, Rio Negro tributary, Amazonas, Brazil

Sponsored by

Brazil, Amazonas, Santa Izabel do Rio Negro

The cardinal neon is the symbol fish of the blackwater rivers and creeks of the Rio Negro Basin, impossible to think of a blackwater biotope aquarium and not think of Paracheirodon axelrodi. The Urubaxi River, located in the middle Rio Negro, municipality of Santa Izabel do Rio Negro, is one of the main collecting points.

The biotope project was designed to recreate the underwater landscape of the river, from the perspective of a diver facing one of the banks, looking at the river bank, with its roots and trunks exposed, part of the flooded forest, responsible for the great amount of organic matter present in its waters, dyeing them black, which further highlights the colors and iridescence of the neons.

A background composed of coconut fiber and roots, many leaves and seeds in the background and a large trunk, in addition to aquatic plants and ferns growing on the bank make up the habitat of the cardinal neon and other species, such as Petitella bleheri, also present in this project.

Submitted by
Marco Antonio Cunha
Approved by
Roberto E. Reis & Flávio Lima
-0.5244321, -64.8214188
Geographical region
South America
Drainage Basin
Amazon basin
River catchment
Rio Negro
Water body type
Water body name
Rio Urubaxi
Water body part
Flood plain
Water body course
Middle 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
28 °C
Water flow/curent

Chemical parameters

4 mg/l
Dissolved Oxygen

Aquarium information

Aquarium description

Set-up date
February, 2022
Aquarium decoration

Substrate composed of 8 kg of light beige river sand, fine granulometry, in addition to many botanical elements such as buriti seeds and bark, a typical tree from the Amazon region, a small dry coconut husk, coconut husk fiber and many tree leaves, dried fruit, simulating what we see on the underwater images of the Amazonian streams. All this organic matter releases a lot of tannin, leaving the water naturally dark, in addition to lowering the PH, keeping it around 6.0.

The rear background is molded in expandable foam, all covered with dry coconut fibers and with several tree roots, so it looks like we’re looking at the river bank, providing a different perspective. I also added some moss and filamentous algae, making the environment more welcoming for the fish, constantly swimming through the roots. At the top, I planted some ferns, which are rising to the surface and putting their roots into the water.

Composing the aquatic habitat, a large trunk as if it were one of the numerous trees that spend part of the year partially submerged, during the period of the Amazon rains and floating plants typical of the Amazonian rivers, Pistia stratiotes and Salvinia auriculata.

Aquarium equipment

The lighting consists of three spots of Stella LED lamps, par 20, opening angle 25º, directional, cold white 6500K, with 5.5W each, totaling 1,650 lumens and luminous intensity of 4,050cd.

The filtration system is made by a Jebo brand canister with a capacity of 900 l/h with two liters of Oceantech ceramic media and mechanical filtering blanket.

Fish care

Maintenance is carried out periodically, with TPAs ​​of 20% and monthly cleaning of the canister, as the large amount of tannins present in the water heavily soils the mechanical filtering element.

Parameters are measured and adjusted weekly if necessary. The same care is given to the replacement water from evaporation and TPAs, already being kept with some leaves so that it has physicochemical characteristics as close to the water of the aquarium.

The animals are fed once a day, preferably with flocked food specific for tetras, sometimes with garlic or spirulina-based food.


  • Paracheirodon axelrodi
  • Petitella bleheri
Plant care

The plants are not very demanding, only a control is made in the growth so that they do not occupy a very large area of ​​the surface, since they have a very accelerated reproduction rate.

The filamentous algae present in the roots also have to be controlled to prevent them from spreading uncontrollably.

Floating plants:

  • Pistia stratiotes
  • Salvinia auriculata

Wetland plant:

  • Nephrolepis exaltata (Lomariopsidaceae)
Water care

As already mentioned I make monthly partial exchanges of 20%. The make-up water is treated with antichlorine and kept stored with some dry almond leaves, providing a good addition of tannins and acidifying it. To balance the PH and keep it stable I use a buffer. As the aquarium is located outside the house and the climate is hot and with little thermal amplitude, it is not necessary to use heaters or coolers, with the water temperature remaining around 28º C.


80 cm
30 cm
40 cm
96 L

Substrate in aquarium

Stone form
Submerged terrestrial vegetation

Comment by the expert

Roberto E. Reis: Beautiful tank with big piece of wood and planty of roots and moss.

Flavio Lima: The reproduced aquascape seems to be very accurate and almost a perfect reproduction of the original habitat.