Black Ruby Barb (Pethia nigrofasciata)

Pethia nigrofasciata is a Sri Lankan endemic, and a mature male in breeding condition flushes so deep a red-black that the body color genuinely shifts rather than just intensifying, one of the more dramatic mood-and-condition color changes among the barbs. It's also one of the better-behaved members of a family with a real fin-nipping reputation, calm enough to run in a general community rather than a dedicated barb tank. Keep it in a proper group and that breeding flush shows up across the whole school at once.

Care level: Easy · Temperament: Peaceful, shoaling · Max size: ~2.5" · Min tank: 20 gal · Diet: Omnivore, flake/pellet