Brachyhypopomus is a genus of weakly electric knifefish in the family Hypopomidae, part of the Gymnotiformes — the neotropical order that also contains the electric eel as its most famous relative. The atlas lists 29 species, found across Brazil, Peru, Colombia, Venezuela, Guyana, Ecuador, Bolivia, and Paraguay. Members of the genus typically live in slow-flowing or still freshwater — flooded margins, vegetated backwaters, and turbid lowland rivers — and are mostly nocturnal, using a continuously generated weak electric field for electrolocation in the dark rather than for stunning prey. The genus gives its name to the bluntnose knifefish group, and several species in the atlas (B. occidentalis, B. cunia, B. brevirostris, B. diazi) share that common name and a similarly short, rounded snout.
Brachyhypopomus is more a subject of scientific study than an aquarium staple — the genus has been an important model for research into electric-organ-discharge physiology and sexually dimorphic signaling, since males and females of many species produce measurably different waveforms. A handful of species occasionally reach the knifefish specialist trade, kept much like other weakly electric fish: dim lighting, soft cover, and tankmates chosen carefully, since these fish rely on their electric sense and can be sensitive to crowding and to other electrogenic species. Adult size varies widely across the genus, from roughly 4 in up to about 18 in, and most assessed species currently sit at Least Concern, though a large share remain Not Evaluated or Data Deficient.