Retroculus

Retroculus acherontos is a cichlid known only from tributaries of the upper rio Tocantins basin in Goiás state, Brazil. It grows to at least 194 mm and differs from its congeners in developing a nuchal hump in both sexes above about 121 mm SL. Based on its morphology it is hypothesised to be less rheophilic than other Retroculus, and it has been collected in small to medium-sized tributaries with clear or sediment-filled water.

Retroculus lapidifer is a rheophilic cichlid from the rio Tocantins and Araguaia systems and nearby coastal drainages of northeastern Brazil. It lives in rapids and fast-flowing stretches of clear water rivers, and needs a set-up designed to resemble a flowing river, with a base of at least 210 by 60 cm and water of 26 to 32 °C. A biparental substrate-spawner, it has been bred in aquaria and is available in the trade on a sporadic basis.

Retroculus xinguensis is a rheophilic cichlid from the rio Xingu basin in Brazil, with a handful of records from the Tapajós drainage. It occurs in rapids and fast-flowing stretches of clear water rivers, and differs from its congeners in having conspicuous dark bars on the caudal fin. It is available in the trade on a sporadic basis and needs a large set-up designed to resemble a flowing river, with water of 26 to 32 °C.