The redtail catfish, Phractocephalus hemioliopterus, is a pimelodid (long-whiskered) catfish named for its orange-red caudal fin. In Venezuela it is known as cajaro and in Brazil it is known as pirarara. It is the only extant species of the genus Phractocephalus. This fish originates from South America in the Amazon, Orinoco, and Essequibo river basins. Despite reaching 1.8 m (5 ft 11 in) in length and 80 kg (180 lb) in weight, this fish is a common aquarium fish.This fish also has a hybrid with the Tiger Shovelnose Catfish.

 

The redtail catfish is an extremely popular fish in Amazonian themed exhibits at public aquaria, where they are often housed with other large fish such as Colossoma macropomum, Arapaima gigas, and other large catfish.Juveniles are often available as aquarium fish despite their eventual large size. In an aquarium where they may be well-fed, these fish can grow quite rapidly. Weekly feeding is appropriate for this catfish; overfeeding is a common cause of death in this species. It feeds heavily on live and dead fishes and other meat. Even as a juvenile of only a few inches in length, they are able to swallow many of the more common aquarium fish such as tetras, and it is only appropriate to house this fish with other species of relatively large size. Redtail catfish also have a habit of swallowing inedible objects in the aquarium. Though these are often regurgitated, both the swallowing and the regurgitation can present a problem for the fish, and these objects are best kept out of the aquarium. It is important that these fish are housed in large aquariums. A minimum size tank for a full grown (4-5 feet) is 1000+ gallons.