Redtail Catfish
Phractocephalus hemioliopterus
Min Tank Size
4000L
Adult Size
130 cm
Lifespan
20 years
About
Native to the Amazon and Orinoco river basins of South America, the Redtail Catfish is one of the most visually striking large catfish in the world. Its body is a dramatic contrast of dark grey-brown on the dorsal side and bright white or cream on the belly, capped off with that iconic vivid red-orange tail. Juveniles are absolutely stunning, and that's exactly why they end up in shopping carts at fish stores everywhere, often by people with a 200-liter tank at home.
This fish doesn't just get big, it gets big fast. A juvenile sold at 10-15cm can reach 60-70cm within the first year under good conditions, and adults commonly hit 120-130cm in captivity. Water parameters lean soft and slightly acidic to match its Amazonian origins, with temperatures in the low-to-mid 20s Celsius. Filtration needs to be seriously oversized because the waste output from a full-grown specimen is enormous. Weekly water changes of 30-50% are not optional.
Feeding is straightforward since it's a committed carnivore. Whole fish, prawns, mussels, and large meaty foods make up a practical diet. Feeder fish should be avoided long-term due to disease risk and nutritional imbalance. Pellets formulated for large predatory catfish can be trained onto juveniles with patience and are the cleaner long-term option.
Behaviorally, Redtails are not frantic fish. They cruise slowly, investigate their territory, and spend a lot of time resting near the bottom. But don't let that calmness fool you. Anything tankmate-sized that comes within range is food, full stop. They are built to ambush and swallow.
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Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Redtail Catfish together
Grows to 130cm and will eat anything it can fit in its mouth; most hobbyists simply cannot provide a setup large enough for tankmates.
Compatibility
Realistic tankmate options are extremely limited and tank-size dependent. In truly massive setups (3000 liters or more), large armored catfish like big Plecostomus species can sometimes coexist because they're not worth swallowing and can take some bumping around. Large stingrays have been kept with them in public aquarium settings. Virtually no fish under 40-50cm is safe with a full-grown adult. Pacu and large Arowana have been housed together with mixed results. Invertebrates of any kind are snacks. Honest answer: most Redtail Catfish should be kept alone in the largest tank possible.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The single biggest mistake is buying a juvenile without a plan for the adult. These fish reach display-tank-breaking size in under three years and live for two decades. Filtration has to be commercial grade, think large sump systems with high turnover, not a standard canister filter. Feeding live fish long-term introduces disease and creates behavioral problems. A varied diet of whole prawns, silversides, and quality large-catfish pellets is better. The tank itself needs to be structurally sound enough to hold the water volume, and the floor beneath it needs to support that weight too.
Behavior & Aggression
Redtail Catfish aggression isn't really aggression in the traditional sense, it's predation. They don't chase or harass fish out of territorial spite the way cichlids might. Instead, anything small enough to fit in that enormous mouth simply disappears. Juveniles may tolerate tankmates for months, then one morning they're gone. Adults have mouths capable of swallowing fish you wouldn't expect. Conspecific aggression is also real, two Redtails in the same enclosure will fight seriously, often resulting in injury or death, especially as they mature.
Things to Know
- Grows to 130cm+ and needs 3000+ liters as an adult, not a home fish for most
- Will eat any tankmate that fits in its mouth, including surprisingly large fish
- Produces extreme waste, requires heavy commercial-grade filtration
- Long-lived (20+ years), a serious decades-long commitment
- Sold as tiny juveniles but reaches adult size within 2-3 years
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