African Knife-fish

About

The African knifefish (Xenomystus nigri) is one of the more characterful oddball fish you can keep, and arguably the most beginner-accessible of the knifefishes. Native to a huge swath of tropical Africa including the Nile, Congo, Niger, and Chad basins as well as various coastal river systems in West and Central Africa, it favors slow, heavily vegetated water where it can lurk out of sight through the day. What immediately sets it apart from other knifefishes is the total absence of a dorsal fin. A handy way to distinguish it from the similar-looking Asian knifefish Notopterus notopterus. Instead, it propels itself with a long undulating anal fin that runs the length of its underside, fused with the caudal fin, and this arrangement lets it glide smoothly in reverse just as easily as forward. It's also an obligate air-breather, periodically surfacing to gulp air through a swim bladder modified for gas exchange, often producing a soft bell-like sound as it does so. During courtship, pairs communicate with audible barking sounds. Genuinely unexpected from an aquarium fish. Nocturnal by nature, it can be shy at first but tends to grow bolder with time. It is scaleless and sensitive to medications, so dose carefully. Adults become territorial with their own kind, and anything small enough to eat will be eaten.