Charax is a genus of predatory characins in the family Characidae, distributed through river systems of tropical South America; the atlas draws records from Brazil, Guyana, Peru, Colombia, Venezuela, Suriname, and Argentina. They have a laterally compressed, often glassy or silvery body, a large mouth armed with well-developed teeth, and — like their headstander-associated relatives — a resting posture with the head tilted downward. Charax are ambush predators of smaller fish and invertebrates in open water and along vegetation edges, and their body plan and coloration lean toward camouflage and speed rather than the bright ornamental patterns of typical tetras. Adult sizes run larger than most characins in the atlas, from roughly 3.3 up to 7.5 in depending on species.
The best-known aquarium species is Charax gibbosus, the Glass Headstander, kept by specialist characin fans for its translucent, humpbacked profile and distinctive resting angle rather than by general hobbyists; a handful of other species circulate in the predatory-fish trade under similar common names. Because they are genuine predators, Charax need tankmates too large to be eaten, a diet leaning toward live or meaty frozen foods, and enough swimming room for an active mid-water fish. Conservation status across the genus looks stable — most assessed species are rated Least Concern, with the remainder Not Evaluated rather than flagged as threatened.