Pachypanchax is a genus of egg-laying killifish (family Aplocheilidae) restricted to Madagascar and the Seychelles, an Old World lineage in a family otherwise dominated by African and Asian genera. Atlas species run 2–4 in, more robust and heavier-bodied than many killifish, with the elongate body, flattened head, and upward-facing mouth typical of surface-dwelling predators that pick insects and small prey from the water's surface.
Playfair's panchax (P. playfairii), from the Seychelles, is the genus's long-standing aquarium representative — one of relatively few Old World killifish to become an established, hardy community-tank fish, tolerant of a range of water conditions though males can be territorial. The Madagascar species, including Arnoult's panchax (P. arnoulti) and the Madagascar panchax (P. omalonotus), are far less familiar in the hobby and far more urgent conservation cases: five of the atlas's seven species rank Endangered and one Vulnerable, reflecting the severe pressure Madagascar's freshwater fish face from habitat loss and introduced predatory and competing species. Six of the seven species carry CARES conservation-priority status in the atlas, underlining how much of this genus sits close to the edge.