Aba Aba Knifefish (Gymnarchus niloticus)

The Aba Aba Knifefish (Gymnarchus niloticus) is one of the most extraordinary and demanding freshwater fish in the hobby. Native to the vast river and lake systems of tropical Africa including the Niger, Congo, Nile, and Chad basins, this ancient species propels itself exclusively using a long undulating dorsal fin while holding its body rigid — an unusual locomotion linked to its electrosensory system. Gymnarchus generates a continuous weak electric field through modified tail muscles and detects distortions in this field caused by nearby objects, prey, and conspecifics. In nature it reaches over 160cm and can exceed 20kg. In captivity, specimens of 80–100cm are common in large public aquarium exhibits. Its predatory nature means any fish small enough to be swallowed will be eaten, and its electric sensitivity makes it intolerant of conspecifics and other electric fish. Only professional aquarists with thousands of litres of filtration capacity should consider keeping this species.

Requires an enormous aquarium of at least 2,000 litres with powerful filtration and heavy water changes. Feed large live or freshly dead fish, whole prawns, earthworms, and meaty foods two to three times per week. Keep individually — conspecifics and other electric fish will be attacked. Provide a large dark hide. Water conditions should be warm (24–28°C), slightly soft and acidic to neutral. Not suitable for community tanks under any circumstances.