The ropefish, Erpetoichthys calabaricus, is a species of freshwater fish in the bichir family and order. It is the only member of the genus Erpetoichthys. It is native to West and Central Africa. The ropefish possesses a pair of lungs in addition to gills, allowing it to survive in very oxygen-poor water. The ropefish inhabits slow-moving or standing, brackish or fresh, warm water at temperatures of 72–82 °F. It occurs in Benin, Cameroon, Nigeria and possibly the Republic of the Congo, spanning the area from the Ogun River to the Chiloango River.
The ropefish reaches a maximum total length of 15 in. They are nocturnal, and feed on annelid worms, crustaceans, and insects. When moving through water slowly, it tends to use its pectoral fins, changing to an eel-like form of swimming (making more use of full-body movements and the caudal fin) when moving quickly. Both in the wild and in captivity, ropefish are known to explore land if given the opportunity, slithering along like a snake and also taking food items on land.
They are inquisitive, peaceful, and have some “personality”. Although nocturnal, ropefish will sometimes come out during the day. Since they have a peaceful nature, other fish may “bully” a ropefish, despite its large size, especially in competition for food or space. Some ropefish also have an inclination to stay close to the water surface, where they will be safe from other fish and will even allow most of their bodies to leave the water at times.
They can be difficult to keep; they will jump and enter pumps to escape tanks and frequently die as a result, and they can be sensitive to pH swings and nitrogen chemistry. They will often consume other smaller fish when given the opportunity. Often small feeder goldfish and minnows are eaten in place of bloodworms or nightcrawlers, and other commercially available live fish food.