All fish / Gymnarchidae

Aba Aba Knifefish

Gymnarchus niloticus

Also known as aba aba, aba, african knifefish, frankfish, gymnarchus, freshwater rat-tail, nile knifefish, ปลาไหลไนล์, ギュムナルクス・ニロティクス, ギムナーカス, 尼罗河魔鬼, 裸臀鱼

This is a long, eel-like fish with a pointed snout, no tail fin and no pelvic or anal fins. It swims by rippling a very long dorsal fin that runs along most of its back, so it can glide forwards and backwards with ease. Keepers of large predatory fish value it for that unusual way of moving and for its weak electric field, which it uses to find its way and to sense prey.

Care at a glance

Care level

Hard

Temperament

Aggressive

Adult size

90 cm

Temperature

23 to 28 °C

pH

6.5 to 7.8

Smallest tank

2000 litres

Keep as

Keep singly

Diet

Carnivore: fish, prawns, earthworms, mussel and large frozen foods

Swims

Middle of the tank

Lifespan

10 to 20 years

Water

Freshwater

Wild range

Nile, Chad, Niger, Volta, Senegal and Gambia basins and Lake Turkana, Africa

Breeding

In the wild, pairs build a large floating nest of plant material in swampy shallows and guard the eggs and young aggressively. It has not been bred in home aquariums.

Good to know

Juveniles are sold small, but adults commonly reach about 1 m and can grow to well over 1.5 m. They are very aggressive and will bite, so only a huge tank or public aquarium can house one, and it must be the only fish in it.