Redtail black shark

The redtail black shark is a freshwater cyprinid (family Cyprinidae), not a true shark, endemic to Thailand and now considered critically endangered in the wild while common in the aquarium trade. It has a jet-black, torpedo-shaped body contrasted by a vivid red tail fin. It is a territorial and often aggressive fish, particularly toward its own kind and other bottom-dwellers. It is best kept singly in a spacious community tank, as multiple individuals usually fight unless the aquarium is very large. Providing caves, driftwood, and dense planting gives it a territory and breaks up sightlines, reducing aggression toward tankmates. It is an omnivore that grazes on algae and biofilm and accepts sinking pellets, vegetables, and frozen foods. Suitable companions are active, robust mid- and upper-water fish that avoid its claimed floor space.