African Knifefish, Xenomystus nigri

The African brown knifefish or African knifefish (Xenomystus nigri), is the only species in its genus. It inhabits the Chad, Nile, Congo, Ogowe, Niger, Sierra Leone, Liberia, Togo, Benin and Cameroon river basins. Slow moving water with vegetation is its preferred habitat.

In an aquarium it will hide when there is light present. They may feed on smaller fish in the tank and can become aggressive to other knifefish as they age.

The body of the African knifefish is long and flat similar to a knife blade. The anal fin (bottom fin near the rear) runs from under the gill opening on the under side of the fish and is fused together with the caudal (tail) fin. The pelvic fins (pair of fins lower center of body) are small and not used for movement. It has no dorsal fin (top fin) and the pectoral fins (pair of fins by gill) are long used for controlling its movement, often by a swirling motion.

The knifefish has extremely small scales giving it a smooth appearance except for a lateral line that is used as an extra sensory system. It uses nerve-filled pits along its body for navigation in dark water and it has large eyes disproportionate of the body, allowing the fish to have excellent night vision.

It has a large mouth and a pair of short whiskers used for hunting. The knifefish will swim with its head toward the bottom using the whiskers along with its eyes to search for food. Its diet consists of worms, crustaceans, insects and snail.

Special features of the African knifefish is it can make barking sounds and surfaces periodically to take in air.

Female knifefish can lay as many as 200 eggs that are about 0.08 inches in diameter.

Image Caption: African knifefish (Xenomystus nigri). Credit: Haplochromis/Wikipedia (CC BY-SA 3.0)