Redtail catfish

Phractocephalus hemioliopterus

Also known as RTC, Redtail cat

FreshwaterFish

Redtail catfish (Phractocephalus hemioliopterus) — Mattia Nocciola · CC BY-SA 4.0

Care at a glance

Temperature: 68–79°F (20–26°C)
pH: 6.0–7.5
Adult size: 39.4 in (100 cm)
Minimum tank: 1,506 gal (5,700 L)
Temperament: Aggressive
Social behavior: Solitary
Swim level: Bottom
Difficulty: Difficult
Breeding: No record
Rarity: Common
Origin: Amazon and Orinoco basins
Family: Pimelodidae

Overview

Check your local rules before buying one, since this fish is restricted or banned in some places, and never release it into the wild. This is not a fish for a normal home aquarium. It needs a minimum of 5700 liters, kept at 20 to 26 C and pH 6 to 7.5, with a bare bottom or large smooth pebbles since it will swallow gravel that fits in its mouth. Keep it alone or only with similarly huge fish, because it is aggressive and territorial and will eat any tankmate small enough to fit in its enormous mouth. Feed meaty foods like whole fish, shrimp, and prepared pellets sized for large predators, and keep it bottom focused, where it sits and waits.

In the wild

Redtail catfish come from the big main rivers and flooded forests of the Amazon and Orinoco basins, where they cruise open bottom in slow, warm water. To match that, give them a cavernous bare bottom tank measured in the thousands of liters, with oversized filtration to keep up with the waste a fish this size makes. Keep the water warm at 20 to 26 C and roughly neutral, pH 6 to 7.5. There is no planting or aquascaping to speak of here, just open swimming room and rock solid water quality.

Good to know

This is a large catfish in the family Pimelodidae, and it is a true monster, reaching about 100 cm and often 90 to 120 cm in captivity. It grows fast from the cute juvenile sold in stores, so the small size you buy is gone within a year or two. There is no reliable record of it breeding in home aquariums. With the right space it can live for many years.

Did you know

The mouth is the whole story with this fish. It is wide enough to swallow prey nearly as large as its own head, and in the wild it eats fish, crabs, and whatever else it can get down. That is exactly why a small tankmate that looked safe one week can simply be gone the next.