Which freshwater fish is known as the black ghost knifefish?

Apteronotus albifrons is the freshwater fish known as the black ghost knifefish.

This unusual fish is native to freshwater habitats in South America, including parts of the Amazon and Orinoco basins. Its dark, laterally compressed body and long undulating anal fin give it a distinctive appearance. It lacks a conventional dorsal fin and uses its anal fin to move smoothly backward and forward.

The black ghost knifefish produces a weak electric field for sensing its surroundings and communicating. This electrosensory system helps it navigate in murky water and locate prey, but it is not the powerful electric discharge associated with electric eels.

It is often confused with other knifefish sold in aquariums. The black ghost knifefish is Apteronotus albifrons; the unrelated glass knifefish and banded knifefish belong to different genera.