Can Oscar Fish Live With Redtail Catfish?

Both oscars and redtail catfish have the same problem. Many pet shops sell these fish as tiny youngsters, not informing their new owners that these fish can quickly grow to be more than a foot in length. However, despite their similar growth patterns, these fish do not make good tank mates.

  1. Oscars

    • The oscar is a large cichlid from South America. Due to floods at fish farms and released aquarium pets, the oscar has become established in other areas, including the Everglades. This fish can grow larger than a foot in length. They do best in soft, acidic water, although they can adapt to a wide range of conditions if they must. They typically reach their adult size in less than a year, growing from tiny, inch-long youngsters.

    Redtail Catfish

    • The redtail catfish (Phractocephalus hemioliopterus) also hails from South America. Like the oscar, pet shops sometimes sell small specimens. However, these fish grow even larger than the oscar, sometimes reaching sizes greater than 4 feet. Unlike many catfish, the redtail is not a sedentary bottom-dweller. These catfish cruise in open water, swimming actively. Their bodies have a vaguely shark-like shape to them, an adaptation for their active -- and predatory -- lifestyle.

    Predation

    • The main reason you should not keep these fish together is predation. In most aquariums, oscars' large size allows them to prey on smaller fish. But the redtail catfish is one of the few aquarium species that gets large enough to eat oscars, growing more than four times the size of an adult oscar. Though oscars are ornery enough to fend off most predators, redtail catfish can usually eat oscars without much trouble within the confines of an aquarium.

    Accommodations

    • On top of the issue of predation, redtail catfish present additional challenges. In order to keep a group of oscars, you need a large aquarium -- in the ballpark of 360 gallons if you want to keep more than one. While this is on the large end for a home aquarium, the redtail catfish needs a tank an order of magnitude larger. An aquarium of at least 2,700 gallons is recommended for redtail catfish, and this is on the small side of ideal. Because of this, accommodating a redtail catfish is almost impossible for the home aquarium. Public aquariums are a better home for them.