Fallen trees have opened a light gap around a rainforest stream. Careful examination will reveal a substrate of rocks. Lots of wood and tree branches are present in the stream, providing shelter for fish.
A biotope aquarium is set-up to simulate a natural habitat. The fish, plants, water chemistry, light conditions, and tank furnishings are similar to those that can be found in a specific natural setting.
RAINFOREST STREAM IN SOUTHWESTERN PERU
The southeastern part of Peru is arguably the most biodiverse place on the planet. This biological wealth extends to the river systems found in this tropical rainforest environment.
This biotope profile will look specifically at a rainforest stream flowing into the Madre de Dios River.
Small rainforest streams are common in this part of Peru. They generally arise from springs and range in width from a few inches to 10-14 feet according to Amazon Headwaters. Rainforest streams in the region rarely exceed 3 miles (5 km) in length.
Rainforest Stream Characteristics
Depth: Depth ranges from a few centimeters to rarely more than 5 feet (1.5 m).
Temperature: Temperature is relatively constant due to shading by the forest canopy. Streams are roughly 1-2 degrees cooler than river channels.
Water chemistry: According to Amazon Headwaters, there is high variation of water chemistry between streams. In their survey, the authors found the pH to range from 3.8-4.9 while conductivity was 10-15. pH and conductivity rise during the low water period, possibly due to "increased phytoplankton production." Water transparency also increases at this time.
Oxygen levels: Oxygen concentrations are generally high but fall slightly when large quantities of organic matter are present.
Substrate: The substrate consists of mud or sand with overlaying organic matter and vegetation in varying states of decomposition. There is a large amount of submerged wood and in some areas, especially fast-flowing sections, there may be a cover of pebbles and stones.
I observed very few aquatic plants in the rainforest stream -- especially in shaded areas where very little light penetrate the dense canopy. In a unshaded pool section an Amazon sword plant (Echinodorus sp.) was present along with a grassy Vallisneria-like plant. There were plants growing with roots submerged but leaves emersed in some sections of the stream. It is a different case in the nearby forest "swamp ponds."
Surrounding vegetation: The stream is surrounded by rainforest.
Tank size will depend on the type of fish you plan to keep in your biotope aquarium. If you are going with smaller tetras, catfish, and Apistogramma then you can use a smaller tank than if you plan to go with larger cichlids.
Current: Current ranges from very slight to moderate (in shallow areas with a pebble substrate). If you are going for a "stream pool" effect then direct filter outflows to moderate water current.
Lighting: Rainforest streams are generally shaded by an overhead canopy minimizing plant growth and resulting in dark conditions. However, in "light gaps" where trees have recently fallen, sunlight is quite bright. If you want to model your biotope after an exposed area then you could use bright overhead lighting.
Layout: Few plants, lots of wood, and open swimming areas are recommended.
Substrate: Fine gravel or sand overlaid with pebbles and rocks.
Other notes: You might consider using some peat moss in your filtration system to reduce the pH and soften the water. Peat moss can also mimic the slightly tea-colored water conditions that result from decaying vegetation.
Fish suitable for aquariums
The rio Madre de Dios probably has more than 600 species, many of which have yet to be described according to Amazon Headwaters. Detritus-feeders, invertebrate-feeders, and seed- and fruit-eating species are abundant in the system.
The aquarium fisheries trade began in the department of Madre de Dios in 2002 according to Amazon Headwaters. The book says the rio Madre de Dios headwaters regions has advantages when compared with aquarium trade fisheries in other parts of the Amazon, namely that the seasonal high water period is "neither too deep nor too long to prevent aquarium trade fisherman from working during the rainy season. Elsewhere in the Amazon Basin aquarium trade fisheries largely stop during the flooding season." Further, the rio Madre de Dios watershed had a large number of endemic species, some of which are small and decorative enough to be attractive as aquarium fish. The book lists the following genera as promising for the aquarium trade: Abramites, Corydoras, Pterolebias, Apistogramma , Crenicichla, Mesonatua, Carnegiella, Gymnocorymbus, Hemigrammus, Tyttocharax, Tyttobrycon, Pyrrhulina, Ancistrus, Hypostomus, Pimelodella, and Pimelodus.
The following fish were observed in the rainforest stream:
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"Rainforest" is used interchangeably with "rain forest" on this site. "Jungle" is generally not used.