Although it does penetrate the lower basins of rivers, particularly the Amazon where it has been collected from the rio Xingu several hundred kilometres from its mouth, this species is predominantly an inhabitant of mangrove swamps, estuaries, and other such saline habitats.

It is particularly common in tidal channels, shallow inshore lagoons, and the lower reaches of rivers.

This species has been referred to the genera Poecilobrycon and Nannobrycon in the past and in the aquarium hobby is also known as ‘oneline’ or ‘red fin’ pencilfish. It’s a popular aquarium fish and has an interesting oblique swimming-style, a behavioural trait shared only with N. eques among congeners.

The most recent diagnosis of the species appears to be that giv…

A. bimaculatus is not a popular aquarium fish but is available on occasion exception, most often as a contaminant among shipments of other species.

It’s identity is also in question to an extent with the name currently applied to what is considered to represent a species complex comprising at least four taxa.

Despite the ubiquity of its name in aquarium literature, confusion surrounds its true identity. Given it’s the only member of the genus occurring on the island, fish from Trinidad do presumably represent C. aeneus (see our image), but the classification of those from other localities appears far from certain.

Today the species is accepted to occur throughout much of South America, and indeed similarly-patterned fish do occur across a large portion of the continent. Some of these, such as the gree…

This species was previously known as ‘Aequidens’ pulcher but has been considered s member of the genus Andinoacara since 2009.

This species can be told apart from relatives by the characteristic ‘keyhole’ shaped marking on each side of the body.

It’s one of few fishes in which the current generic name is derived from the common name popularised in the aquarium hobby with ‘Cleithracara‘ a combination of the Greek kleithron, meaning lock, and, acará, the Guaraní word for cichlids.