The zebra knifefish (Gymnotus pedanopterus) is a large fish found in Peru and Brazil where it tends to inhabit sluggish or still waters, and seems to prefer turbid environments. It is also found in the deeper parts of main river channels, and in general is considered a bottom dwelling species. This fish grows to an adult size of up to 12 inches long. There are no distinguishing features between males and females.
Like other Gymnotids, the zebra knifefish produces a weak electric field using specially adapted muscle tissue located towards the tail. It also possesses electroreceptors which allow the fish to receive electrical signals which it can use to sense the tiniest of movements as the field around it is disturbed, and navigate in total darkness. What is most fascinating about this adaptation is that the fish also use it to communicate with each other and find partners.
Zebra knifefish prefer a temperature of 72°F to 82°F. They will do well with a pH of 6.0 to 7.0, and a hardness from 2 to 12°H or higher.
The zebra knifefish is sensitive to many aquarium medications, particularly those containing copper.
Adult zebra knifefish should be maintained in an aquarium of 55 gallons or larger. Juveniles may be maintained in an aquarium of 30 gallons or larger. Keep in mind that floor space is more important than height. Decor is not critical, although it does appreciate plenty of cover. Large stones and pieces of driftwood (ZM2000), twisted roots, and live plants all work well. It is also much more active under dim conditions, so either use weak lighting or add a layer of floating plants to diffuse the light entering the tank. A dark colored soft, sandy substrate (CS6631) is a good choice for bringing out the best color.
Small fish will be eaten by the zebra knifefish, but it can be combined with other similarly sized species in a big enough tank. Do not keep it with anything too boisterous or aggressive or it might become withdrawn. Possible tank mates include large, robust cichlids such as Geophagus sp., larger Characins, Cyprinids, catfish, Loricariids, gouramis, and other species such as bichirs. It is very territorial with conspecifics, and a very big tank would be needed to keep more than a single specimen.
In the wild, the zebra knifefish is a bottom dwelling predator that feeds on insects, worms, crustaceans, and small fish. In the aquarium it may be fed live and frozen foods. Good choices include frozen krill (SF7136), live blackworms, earthworms, and ghost shrimp. For maximum color, growth, and health these fish will look their best when given probiotics (AL169) in addition to a balanced diet.