The porthole catfish or slender catfish, Dianema longibarbis, is a tropical freshwater fish belonging to the Callichthyinae sub-family of the Callichthyidae family. It originates in inland waters in South America, and is found in the Amazon River basin in Brazil and Peru. The fish will grow in length up to 8.2 centimetres (3.2 in). It natively inhabits waters with a pH range of 5.5 to 7.5, a hardness of 2 - 20 DH, and a temperature of 22° - 26°C (72° - 79°F).