H. borealis is a member of the putative ‘H. heterorhabdus-group’ of closely-related species within the genus as proposed by Géry (1977).

There are around 15 members characterised by a ‘longitudinal pattern’ consisting of a thin, usu…

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…

This is the type species of the genus, fairly ubiquitous in the aquarium trade, and represents an excellent choice for the newcomer to fishkeeping since it’s less demanding than most congeners. It’s sometimes referred to as ‘Beckford’s pencil fish’ or ‘brown pencilfish’.

Don’t worry if your fish look different when you switch on the aquarium lights after dark or in the morning as like most Nannostomus species it assumes a cryptic, vertically-barred colour pattern at ni…

This species is uncommon in the aquarium trade although its name is sometimes applied to other species.

It was originally described in the monotypic genus Pseudopristella, and can be distinguished from the vaguely similar Pristella maxillaris by possession of a relatively large (vs. relatively small) humeral spot and having black pigmentation in the anal-fin restricted to the first ray (vs. a prominent distal blotch).

This small species is a popular aquarium fish but there is some confusion surrounding its identity. Two colour forms have been traded, one of which also possesses tiny hooks on the fin rays.

It can be distinguished from congeners by colour pattern; the body is rose-coloured, fins red with no black markings, and the ovoid humeral spot is prominent, measuring around half of the body depth.

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.