Heterocharax is a small genus of characins (family Characidae) from Amazon and Orinoco basin drainages across Brazil, Colombia, Venezuela, Ecuador, Peru, and Guyana. The atlas covers 3 species, all under 2 in, sharing a slim, laterally compressed, glassy-bodied build typical of the smaller tetra-like characins of these river systems.
Heterocharax virgulatus, known as the Blue Flash Glass Tetra, carries the most recognizable common name in the genus and gives a sense of the group's look — translucent-bodied fish with an iridescent flash along the flank. None of the three species has significant standing in the aquarium trade, and detailed ecological data are limited; what is known places them among the smaller schooling or loosely shoaling characins of blackwater and clearwater forest streams. Conservation status leans reassuring where it has been assessed, with two species rated Least Concern and one not yet evaluated.