Hello, I have a 75 gallon tank with 2 3-4 inch fish, one is an Oscar, and The other is a sun catfish. I woke up today and saw that the catfish's fins were frayed. I put a decoration in the tank and let the catfish hide under it for now. Any suggestions?

The oscar is just being an oscar. There isn't much that can be done except either separating them or just hope that the oscar grows out of it.