Slow and deep tributary of lower Paraguay River, Ñeembucú, Paraguay

_th place in Biotope Aquarium Design Contest 2020

Volume: 576 liters
Dimensions: 160x60x60 cm
List of fishes: Gymnogeophagus balzanii, group of 8 adolescent fish
List of plants: n/a
Description of decorations: Round river stones in different sizes, shapes and coulors, with smooth surface like usually found in ecosystems with moving water. The stones provide spaces to hide from tankmates and serve as perfect place to spawn. Fine and rather bright river sand in natural colour variation (0-1mm) like found in this Biotope(1, 0:10) and compatible for any eartheater fish in this size. (2) Some leaves (1, 6:30) and driftwood in different sizes and shapes, like found in this Biotope (1, 4:05). (also serve as spaces to hide).
Description of equipment: external filter JBL cristalprofi e1902 greenline up tp 1900lph, LED light 11w modified with covers on side, no heater
Water parameters: Temperature is from 20°C in Winter to 25° C in summer. ph is about 6,8. gH about 12
Additional info: Water Change once a week about 1/3 of the water.
The covers on the light help to create dark spaces on the sides to hide and give the tank a bit of infinitiy, since you can’t see the edges properly.


Description of the area surrounding the biotope: Paraguay River, is the fifth longest river in South America. It also is the principal tributary of the Paraná River. It rises in the Mato Grosso region of Brazil at 300 meters above sea level. There is the upper course of the river. When leaving Brazil the lower part begins. It crosses Paraguay from North to South and confluences with the upper Paraná river near the boarder to Argentina. The Paraguay river is 2,550 km long.
Paraguay river demarcates parts of the frontiers between Brazil and Paraguay, as well as Pragaguay and Argentina. The Paraguay river for much of its length gets floodes seasonally, which has effect on the flow of the lower Paraná. The Paraguay river varies in rates of flow between source and mouth. The upper Paraguay floods from December to March, the middle Paraguay floods from May to June and the lower Paraguay in February. The river’s flood area reaches some 100,000 square km.
The climate of the Paraguay drainage basin, with an area of 980,000 square km, is hot and humid. Dry winters and heavy rains in the summer are typical. In the eastern part of the paraguay river there is forest as well as grassland along the banks of the river. (3)
Description of the underwater landscape of the biotope: The biotope’s substrate consists of brighter sand. (1, 0:10) In some areas there are leaves and deposits.(1, 6:30)
SInce there are forests and other vegetation with trees, the biotope also got driftwood and other organic matieral.(1, 4:05). Some places, espacially the one closer to the shores in lower depth of water got plants. (1, 5:25) Deeper and darker areas with less light don’t have any plants. Plants do not belong to Gymnogeophagus balzanii’s natural habitat. (6)
There are also stones in different sizes and shapes, mostly round due to the movement of the water. (1, 4:20)
Description of the parameters of the habitat: The lower Paraguay River basin mostly is quite rich in sediments and suspended load. So the water in general is not clear and transparent. Of course this also depends on the season, wether it’s raining season or not. It’s the same with the ph. In the lower Paraguay basin the ph varies from about 6.3 to 7.9.
The temperature of the lower Paraguay basin water systems varies from about 18–26.3° C, depending on the season. (4)
List of fishes and invertebrates occurring in the nature biotope: Ancistrus hoplogenys, Ancistrus pirareta, Astyanax asuncionensis, Astyanax paraguayensis, Astyanax Pellegrini, Cichlasoma dimerus, Coryoras aurofrenatus, (Gymnogeophagus balzanii), Laetacara dorsigera, Lepthoposternum pectoral, Loricaria luciae, Megalechis thoracata, Pimelodella laticeps, Satanoperca pappaterra (5)
List of plants found in the nature biotope: n/a, since Gymnogephagus balzanii lives in deeper and suspended loaded (darker) areas with less light. (6)
Threats to the ecology:
Sources of information:

  1. (2)
  2. (3)
  3. (4) Water characteristics
  4. (5)
  5. (6) Maintenance

Comments of the members of the jury of Biotope Aquarium Design Contest 2020