A single male of the Tequila Splitfin was sampled in 1955 by Miller and Greenbank, but identified erroneously as Zoogoneticus quitzeoensis, with which species it was collected and found sympatrically . Many years later, the mistake was detected, the fish identified as a new species and finally, 43 years after the first capture, described by Webb and Miller.

In 2001, a wild population of this species was rediscovered in a very small spring pool (3 x 4m in diameter). The population there was composed of only a handful of adult fish and a few tens of juveniles (De la Vega-Salazar et al., 2003). In 2007, N. W. Bailey et al showed, that the allelic richness of this population (though it was comparable in size to an aquatic stock) was higher than in any aquatic stock. In 2013 the loss of this population was reported (pers. comm. Domínguez), so there is not much hope that this species is still persisting in the wild.

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.

Hyphessobrycon melanostichos shares a number of similarities with Hyphessobrycon sp. Blue Ribbon. The former can be differentiated from the latter by a lighter set, more streamlined body , smaller humeral spot and also red colouring, which is not present on the Blue Ribbon tetra. Care and maintenance of the two species is however, virtually the same.

Apistogramma commbrae and other members of the commbrae complex can be distinguished from congeners by the conspicuous double caudal peduncle spot. This species may also be polymorphic, with some males exhibiting red and blue markings on the cheeks and a yellow gular region.

It is included in a group often referred to as ‘red-eyed puffers’, which currently contains four recognised species distributed in Indochina and the Greater Sunda Islands. It can be distinguished from C. borneensis, C. irrubesco, and C. lorteti, the remaining members of this group, by the following combination of characters: 11 dorsal-fin rays; 16 pectoral-fin rays; 11-13 anal-fin rays; 11 caudal-fin rays; eyes not bulging above the head; in males dorsal-fin hyaline, black spot on dorsal-fin base present, pectoral-fin base hyaline, anal-fin hyaline with no black spot at base…

An efficient, largely piscivorous, predator with highly protrusible mouthparts. In the aquarium, juveniles can be offered chironomid larvae (bloodworm), small earthworms, chopped prawn, and suchlike, while adults will accept strips of fish flesh, whole prawns, mussels, live river shrimp, larger earthworms, etc. Older individuals do not require feeding on a daily basis, with 2-3 times per week sufficient.