The genus Brachychalcinus currently contains four other species: B. copei (Steindachner 1882) from the rio Madeira and rio Solimões; B. nummus Böhlke 1958 from the Upper Amazon region in Colombia, Ecuador and Peru; B. parnaibae Reis 1989 from the rio Parnaíba basin, and B. retrospina Boulenger 1892 from the Rio Paraguay system.

The group is often referred to collectively as ‘silver dollar tetras’ and tho…

The colour of this species is often so intense that many who first see it for sale assume it to be artificially coloured. It is currently the only representative of the genus known.

Most Astyanax spp. are not popular in the aquarium hobby, though the genus is among the most speciose within the family Characidae. A. leopoldi is no exception in that you’ll rarely see it offered for sale but may find the occasional specimen mixed among other species in shipments of wild fishes from Peru.

Now the only species in the genus Paratilapia, P. polleni is known as the "marakely" to many natives in Madagascar, which means "black fish". As with most Madagascan cichlid species, it is highly endangered in the wild due to habitat destruction and competition from introduced species and all attempts at captive breeding are to be encouraged.

There is still some confusion as to the identity of the "true" P. polleni as there are both large and small-spotted forms…

Endemic to pthe upper Amazon basin in Peru, around the city of Iquitos.

Most Astyanax spp. are not popular in the aquarium hobby, though the genus is among the most speciose within the family Characidae. A. kennedyi is no exception; you’ll rarely see it offered for sale but may find the occasional specimen mixed among other species in shipments of wild fishes from Peru.

This is a truly stunning species that does well in a Tanganyikan community with well-chosen tankmates. It exists in well over 20 colour morphs, too many to list here. Obviously these should not be mixed in aquaria as they will hybridise freely. In nature, it is only the largest dominant males that build nests whilst the subdominant males and females shoal together. The territories of these dominant fish may measure several metres across….

O. nasuta can be distinguished from other members of the genus primarily by the fleshy proboscis-like growth that extends beyond the upper lip. It exists in several different geographical morphs including "Kachese", "Mpimbwe", "Cape Tembwe" and "Chamba", among others. These should not be mixed in aquaria as they will hybridise freely….

This was the first species to be placed into the genus Ophthalmotilapia.

While the surface-dwelling form of this species is fairly unremarkable and rarely-seen in the hobby, the blind form is very popular indeed. The two may have diverged as recently as within the last 10,000 years, with the blind form losing its eyes and much of its pigment. This probably happened because the fish needed better development in other sensory areas. Losing unnecessary and energy-consuming aspects of its physiology allowed it to devote more energy to developments such as increased numbers of taste receptors on the head.

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.