It’s known by various vernacular names including ‘Pirá-pacu’, ‘Pira-pucu’ or ‘Diente de cao’ (central Amazon), ‘Bicuda’ or ‘Uena’ (rio Tocantins), ‘Bicuda’ (rio Tapajós), ‘Aguejeta’ or ‘Picua’ (Venezuela), and ‘Moruwi’ or ‘Pirapoko’ (Guyana).

The entire dorsal-fin base is located anteriorly to a vertical through the anal-fin origin and this character distinguishes it from all other ctenolucids except B. lucius and B. xyrekes.

Apparently this species is polymorphic with body patterning varying significantly depending on locality. Individuals collected from black water habitats tend to be noticeably darker in overall colouration, for example, with this being particularly evident among populations from the Guiana Shield.

The genus Ageneiosus was at one point classified in…

The genus Ageneiosus was at one point classified in the family Ageneiosidae alongside the genus Tetranematichthys, but this was not accepted by all authors. The grouping remains poorly-studied with the last major revision having been conducted by Watson (1990) in his unpublished dissertation, in which A. inermis was included under the currently synonymous name A. brevifilis. It can be separated from the majority of the genus (except A. marmoratus) by possession of a truncate caudal fin, and from…

Although only described in 2006 this species has been known in the hobby since at least 1988 when it was imported to Germany and traded as G. sp. 'Parnaíba'. An undescribed species from the rio Pindaré in Maranhão state usually sold as G. sp. 'Pindaré' is sometimes labelled G. sp. 'Pindaré' (Parnaíba) which has resulted in some confusion but the two do not occur sympatrically and are totally distinct from one another.

This is the type species of the genus Aequidens and has the widest distribution of any member species. It exists in various colour forms depending on locality with variants from Ecuador and Peru being particularly sought after since they develop striking red (Ecuador) or orange (Peru) colouration on the lower part of the jaw, head and anterior portion of the belly whereas those from Brazil tend to have an overall grey/blue/green colouration, for example.

Despite its type status it's long…

Metynnis lippincottianus is occasionally seen for sale, sometimes under the name of "Silver Dollar". It is easily distinguishable from m. argenteus and m. hypsauchen (which are more commonly sold as Silver Dollars) by its spotted pattern, hence the common name. M. lippincottianus shares a common name with m. maculatus but the two can be distinguished as the spots on m. maculatus are more pronounced.

Silver dollars are common and popular fish in the hobby. They are related to piranh…

Native to coastal river systems south of the Amazon delta in the states of Piauí, Maranhão, Pará, and Amapá, northeastern Brazil. It has been recorded from the rios Guamá (including tributaries such as the rio Ararandeua), Maracanã (rio Peixe-Boi), Morcego, Parnaíba, Piriá, Caeté, Turiaçu (rio Jamari), and Mearim (rio Pindaré).

Reports from French Guiana and western Brazil appear to represent cases of misidentification.

Numerous ornamental forms of this species have been selectively-bred for the aquarium trade, some of which include. It has also been assigned the 'A' number A234 under the DATZ system with possibly conspecific, related forms similarly numbered A235, A236, A237, A238, A239, A240, A241 and A242 depending on locality.

The genus Apistogramma is among the most speciose of South American cichlid genera with around 70 species valid at present but many more awaiting description. In addition …

Famed as a rapacious predator capable of rapidly stripping flesh from bone and a danger to any animal entering its native waters, P. nattereri is among the most notorious freshwater fishes in the world. As a result, displays featuring this “bloodthirsty” creature are found in most public aquaria, grisly Hollywood movies have been released, and the species has become popular in the aquarium trade. Little of this infamy is based on factual evidence, however.