Pterophyllum leopoldi can be differentiated from other members of the genus by the presence of up to 11 vertical stripes on the body, though often only the 3 largest, boldest stripes can be seen. This species also shows a dark patch over the operculum.

In adult specimens, a red/maroon hue over the back and fins is characteristic of the species, leading some to believe the most colourful natural form Angelfish.

The name-sake roman nose possessed by the fish is also very distinctive and used as a meristic feature.

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.

Despite being a wholly unsuitable aquarium subject, C. idella is often traded as such, with an albino form having been developed specifically for the ornamental market.

Individuals which have outgrown their aquarium or pond should never be released into natural waters, either, since this species has proven capable of causing serious environmental damage under a wide range of climatic conditions.

Widely-distributed throughout the Amazon, Orinoco, Essequibo, and Tocantins river systems in Brazil, Peru, Bolivia, Ecuador, Colombia, Venezuela, and Guyana.

Type locality is ‘Rio Cupai [= Rio Cupari], Rio Tapajós basin, Amazon River drainage, Pará State, Brazil’.

The genus Centromochlus is diagnosable by members having the proximal anal-fin radials enlarged and fused to each other at the base, forming a single ossified structure.

It’s sometimes included in the putative subfa…

C. carsevennensis has formerly been synonymised with C. arnoldi but was considered separate by Zarske (2011) using the following combination characters: absence (vs. presence) of a silvery-white to white patch in the centre of some of the flank scales in males, particularly in the lower half of the body; absence (vs. presence) of a horizontal dark body bar in nuptial males; absence (vs. presence) of thin black margins in the dorsal, ventral and anal fins; eggs deposited among submerged vegetation (vs. eg…

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.

This species is rare in the aquarium trade but is arguably more suitable for the home aquarium than some of its better-known relatives given its adult size and relatively docile behaviour.

Other vernacular names include ‘Dientón’ (Peru), ‘Perrito’ (Ecuador), ‘Payara-chata’ or ‘Payarin’ (Venezuela) and ‘Icanga’, ‘Minguilista’ or ‘Peice-cachorro’ (Brazil), some of which are also applied to related species.

Vernacular names in Brazil include ‘Cachorra’ or ‘Pirandirá’, although these are also applied to congeners.

It can be told apart from all congeners by the following combination of characters: head and body silvery with dark dorsal surface; an elongate dark blotch posterior to the opercle; dorsal, caudal and anal-fin rays reddish to orange proximally with some individual variation in intensity and tonality; adipose fin dark, with diffuse black pigmentation.