Arapiuns

The Amazon puffer, Colomesus asellus, is a freshwater puffer found throughout much of the Amazon basin, with records north to Guyana and Venezuela. Also traded as the South American puffer or 'SAP', it is told from congeners by a transverse row of dermal flaps across the chin. It lives mostly in well-oxygenated river habitats, is intolerant of organic waste, and forms loose aggregations, so a group of 6 or more is best, away from the general community.

Geophagus sp. 'orange head' is an undescribed cichlid confined to the lower rio Tapajós in Brazil, including its tributary the rio Arapiuns. Now one of the more readily available members of the genus, it has suffered from commercial breeders who do not cull deformed fry. Two forms exist, one misleadingly traded as G. sp. 'Araguaia orange head', and the orange on the head is most extensive in dominant adult males.

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.

The sharphead eartheater, Satanoperca acuticeps, is a cichlid from the central Amazon basin in Brazil, including the lower rio Negro and rio Branco. Relatively rare in the trade, it is sometimes confused with S. daemon and S. lilith but has three dark flank blotches (vs. two in S. daemon, one in S. lilith). Unless breeding it is surprisingly peaceful, and it is very rarely bred in aquaria.

Satanoperca lilith is an eartheater cichlid known only from Brazil, where it is widely distributed along the Solimões/Amazon main channel. Despite that extensive range it is uncommon in the ornamental trade, where it is sometimes called 'one-spotted demon fish' or 'one spot eartheater'. A single dark blotch on the flank separates it from the closely similar S. daemon, which has two.

The dwarf flag cichlid, Laetacara curviceps, is a small cichlid from the lower Amazon basin in Brazil. An established aquarium favourite, it has also been called 'flag acara', 'smiling acara', 'sheepshead acara' and 'blunt-headed cichlid'. Populations differ in the degree of red and blue on the body and fins. It favours clear, slow-flowing water over leaf litter and is a biparental substrate-spawner.