what fish would be compatible with a redtailed shark?

They don't get on too well with other red tails, they say that you can't keep them with pecko's but there totally fine, leopard bush fish ok, clown loaches ok, tiger barbs, kribensis cichlid, cat dick from synodontis to corydoras are all fine, I would avoid silver sharks and Siemense fighters as there fins appear to be flakes, you could get away with a whole other range if you put in the odd bloodworm block or even make your own blocks they are herbivores but they are pretty territorial

angelfish. they're highly poisonous. sharks should know to stay away from it. or another redtailed shark.