Gymnarchus niloticus
The Aba Knife Fish Gymnarchus niloticus is unusual even for a knife type fish. It is one of the largest knife fish reaching up to 5 1/2 feet (167 cm) long (167 cm) and weighing 40 pounds (18.5 kg). Unlike most in this group, the fin that is used for locomotion is on its back instead of its belly. Other common names it is known by include Aba Aba Knifefish, Aba Khife, Aba, Freshwater Rat-tail, Frankfish, and generically as an African knifefish.
The Aba has an electricity producing organ that runs through most of its body. Unlike the Electric Eel, this organ does not generate enough voltage to stun its prey so it is most likely used for navigation and finding food. But like the Electric Eel it is the only species in its genus, and it too uses its electrical field for a variety of things. It helps the Aba Knife identifying objects in the water, including food, and gives it spatial orientation. Males use an electric ‘stereotyped’ communication to court females.
The large size of the Aba Aba Knifefish demands a very large tank, 300 gallons or more, or even an indoor pond. Because it can be very aggressive it does best by itself. I know of one importer that accidentally put a large Aba in a holding tank with a large Discus and in no time at all, the Discus had a big “U” shaped chunk missing from its forehead. It appeared that this chunk had been surgically removed which shows just how sharp an Aba’s teeth are.
Aba Knife Fish are large dangerous fish and should only be cared for in commercial aquariums and by the most experienced fish keepers with the space and financial ability to care for these giants. The Aba Aba is actually not real hard to care for, as far as getting the water right and getting them to eat. They are very aggressive eaters and have been known to attack their owners.
These fish grow very fast and not many homes can accommodate a 5 foot plus aggressive fish. You’ll eventually need a lot of water to house a growing Aba Knifefish. Plan on eventually needing 300 gallons or more to keep one happy and healthy. They are sensitive to some fish medications such as copper and those containing formalin.
Due to the size and aggression of this fish it is really best to leave them for commercial aquariums or hobbyists that have the knowledge, space, and money to properly and safely care for these giants.
The Aba Knife Fish are carnivores, feeding on crustaceans, fish, insects, snails, and frogs in their native environment. Although they will eat insects, shrimp, and crayfish in captivity, the easiest food to feed them is live feeder fish. They can be trained to eat chunks of dead, freshwater fish which will help to keep the food expenses lower than if you exclusively feed live feeder fish. Some young Aba’s have been known to take flake foods, but this is a rarity.