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Gymnarchus niloticus, commonly known as the aba, aba aba, frankfish, or African knifefish, is the only species in the family Gymnarchidae within the order Osteoglossiformes. It is found exclusively in swamps and vegetated river edges along the rivers Nile, Niger, Volta, Chad, and Gambia.
Description and biology

The aba has a long and slender body, with no caudal, pelvic, or anal fins. The dorsal fin is elongated, running along the back of the fish towards the blunt, finless, tail, and is the main source of propulsion. It grows up to 1.6 metres (5.2 ft) in length and 19 kilograms (42 lb) in weight.[1]
The aba is nocturnal and has poor vision. Instead, it navigates and hunts smaller fish using a weak electric field similar to that of the related elephantfish. Also like the elephantfishes, it possesses an unusually large brain, which is believed to help it interpret the electrical signals.[1]
Abas lay their eggs in floating nests up to a metre across. The adults continue to guard the young after hatching.[1]
The Gymnarchus niloticus fish can make its tail negatively charged with respect to its head. This produces a symmetrical electric field around its body. Nearby objects distort this field, and the aba can sense the distortion on its skin.

The Aba Knifefish, also called the Aba Aba Knifefish, is unusual even for a knife type fish. It is one of the largest knives reaching up to 5 1/2 feet long. Unlike most in this group, the fin that is used for locomotion is on its back instead of its belly. It 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.

Its large size demands a very large tank or even an indoor pond and 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.

This fish can be considered dangerous because a big specimen could easily remove a careless person's finger! If after all I've just told you, you still think you are prepared to handle one of these fish, don't buy the tiny ones that still show their yolk sack because they are very weak at this size. The minimum size to buy is about 3 inches and bigger than this is better.

ABA Aba Knifefish are found in in the Nile, Niger, and Gambia basins in Africa.

These fish get huge up to 5 ½ feet long and up to 40 pounds.

Water Conditions:
Temp: 74° - 82° F (23 - 28°C)
pH 6.5 - 8

Sexual differences are unknown.

Has not been bred in captivity.

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