Is my catfish killing my other my other fish?

Question

I recently bought 3 fish a sunset platy an alge eater and a catfish now all but the catfish has died

Answer 1

Many Catfish, depending on the species, will eat other fish and also eat dead fish. Some Catfish like Cories wouldn't bother other fish, but Pictus Catfish would certainly eat any fish that would fit in their mouths. Also, it is very possible that your other fish died, and then the Catfish ate the corpses. Update your question with the species of Catfish.

Soop Nazi

Answer 2

I've seen a loricariidae or loricarioidea sticking to the side of a gold fish and after a few days the gold fish is dead.