Temperament
By day a redtail mostly rests on the bottom, taking the occasional lap of the tank. It does not chase other fish for sport. But anything that fits in its mouth is food: one 16 inch redtail ate six tankmates in a week.
Tankmates
Large doradid catfish such as Oxydoras niger and Pterodoras granulosus make good tankmates. Most common tank busters are small enough to be eaten. In a big enough system, redtails live for years with arapaima, jau, piraiba, pacu and paroon sharks.
Redtails together
Redtails are territorial toward each other and toward other large pimelodid catfish. Groups of four to ten can live together peacefully for long stretches, with occasional fights that tear tails and barbels. Some of what looks like fighting is courtship: a female pulling a male by the tail is testing a mate.
Hand feeding
Many redtails learn to take food from a hand, and it is one of the joys of keeping one. Some learn in days and some take months.