Poecilocharax is a genus of small characins in the darter family Crenuchidae, native to blackwater and clearwater streams across the Amazon and Orinoco basins. The atlas's records span Brazil, Colombia, Guyana, Peru, and Venezuela. The four species are tiny, with adults reaching only about 1–2 in, and like other crenuchids they are bottom-oriented, non-shoaling fish that spend much of their time perched near leaf litter and submerged wood rather than swimming in open water — a habit that has earned some relatives in the family the 'darter' name.
The blackline tetra (Poecilocharax weitzmani) is the genus's best-known aquarium representative, valued by characin specialists for the male's sailfin-like dorsal and anal fins and a bold black lateral stripe, and typically kept in a soft, acidic blackwater setup with leaf litter and dim lighting that mirrors its native habitat. The other three species — P. bovalii, P. callipterus, and P. rhizophilus — are seen far less often in the trade. Conservation status is a live concern in this genus: the atlas records a Vulnerable rating alongside two Not Evaluated species and one Least Concern, underscoring how little formal assessment small, localized blackwater characins like these have received.