Butterfly Barb

About

Found darting over gravel beds in clear, fast-flowing streams and rivers across the Chao Phraya and Mekong basins, Opsarius pulchellus is a sleek, pelagic cyprinid that goes by several trade names in the hobby. Butterfly barb, mackerel barb, royal opsarius, and green-barred danio among them. It can be identified by the series of seven to ten elongated vertical bars along each flank, which become more rounded toward the tail end, along with a relatively high lateral line scale count compared to related species. In the wild it feeds heavily on insect larvae, and in the aquarium it translates that energy into vigorous, competitive feeding behavior. This is not a fish for a relaxed community setup. It is an exceptionally quick swimmer that can easily intimidate or outcompete slower, shyer species at feeding time, and small fish may be at risk of predation. Good tankmates include robust, similarly sized pelagic cyprinids like Dawkinsia or larger Devario, with bottom-dwellers such as Botia, Garra, or Schistura rounding things out. Despite being social, this species forms a pecking order rather than a cohesive school, so keeping five or more individuals is important to spread any aggression. A group of fewer than three often results in persistent bullying of subordinate fish.