Borneo Sucker

About

Found clinging to rock surfaces in the fast-flowing streams of western Borneo, Gastromyzon ctenocephalus is a compact hillstream loach that rarely exceeds two inches in length. Its body is dark brown to black, peppered with evenly spaced cream spots, and what really sets it apart from close relatives is the presence of iridescent blue spots and streaks in the dorsal and caudal fins. A detail easily missed in a busy fish store display. It often turns up in mixed shipments under catch-all labels like 'Borneo sucker' or 'butterfly loach', so confirming the species can take some careful observation. Like all gastromyzontids, its paired fins are oriented horizontally and its pelvic fins are fused into a suction structure, letting it grip smooth rocks in powerful currents rather than swim freely in open water. It grazes its way across surfaces rather than darting about, which makes for a fascinating tank inhabitant once settled. Despite being listed as aggressive and territorial, much of that behavior centers on competition for prime feeding spots, and the fish generally coexists fine with peaceful, similarly-sized species. Keeping a group of four or more brings out more natural social behavior. Replicating strong water movement and high oxygenation is essential. This is not a forgiving species for a stagnant or poorly maintained setup, so it suits keepers with some experience running high-flow systems.