Red-tailed Black Shark

About

Found across an enormous stretch of Southeast Asia, this large cyprinid, Cyclocheilos enoplos, ranges from the Mekong basin in Laos, Cambodia, and Vietnam westward through Thailand and down into Peninsular Malaysia and beyond. It is a genuinely massive fish, routinely exceeding two feet in length at maturity, with an elongate body and a notably large, long dorsal-fin spine that helps distinguish it from the closely related Cyclocheilichthys species it was once grouped with. The taxonomy around this genus has had a bumpy history, with various reclassifications and synonymy disputes going back to Bleeker in the 1800s, though its current placement in the revalidated genus Cyclocheilos is now generally settled. In terms of temperament, it is relatively peaceful toward tankmates that are too large to be viewed as a meal, which is a sensible caveat given its size. Despite being technically listed as beginner-level in terms of water chemistry tolerance, the sheer adult dimensions of this species make it wholly impractical for the vast majority of home aquariums. It is rarely seen in the ornamental trade, and honestly that is probably appropriate. This is a fish better appreciated in a large public exhibit or left to the wild rivers it calls home.