Melanocharacidium is a genus of darter characins (family Crenuchidae) from South American forest streams, recorded here from Venezuela, Brazil, French Guiana, Guyana, Colombia, Suriname, Bolivia and Ecuador. Rather than schooling in open water like most characins, these are small, elongate, bottom-hugging fish that perch on the substrate propped on their pectoral and pelvic fins in the current — much like a true darter or a goby, a convergent lifestyle that gives the group its common name. The atlas covers 9 species, from about 1.5–4 in, most of them narrow-range stream specialists rather than widespread river fish.
The genus is of far more interest to ichthyologists studying Neotropical stream-fish diversity than to the aquarium trade — only Melanocharacidium depressum carries a widely used common name, darter characin, and the rest are essentially unkept outside specialist collections. Where care notes exist they follow the darter-characin pattern: clear, well-oxygenated, moderately flowing water over sand or fine gravel, and small live or frozen invertebrate foods taken off the bottom rather than from open water. Conservation status is poorly resolved for most of the genus — six of the nine species the atlas tracks are Not Evaluated and one is Data Deficient — but one is assessed as Critically Endangered, a reminder that some of these fish are tied to a single small stream system.