Piabucus is a genus of slender, silvery characins found across a broad swath of South America, with atlas records spanning Peru, Bolivia, Brazil, Venezuela, Argentina, Colombia, Ecuador and French Guiana. The atlas covers 3 species, and at 4–5 in they run considerably larger than the small tetras most aquarists picture when they hear the family name. The body is strongly laterally compressed and elongated, with an upturned mouth suited to feeding near the water's surface, a build shared by several other surface-oriented characins that patrol open water in large rivers and floodplain habitats.
The genus is more a subject for regional ichthyology than for the aquarium trade: Piabucus dentatus (the piabuco tetra) and Piabucus melanostoma (the black chin tetra) have picked up hobby-style common names, while Piabucus caudomaculatus remains essentially unknown outside scientific literature. All three species carry a Least Concern IUCN status, and none are tracked under CARES, consistent with a genus that is widespread across major South American river systems rather than narrowly restricted. Detailed aquarium husbandry data are sparse, and given their size and open-water habits these are not typical nano-tank fish.