I have a discus and a piece of its dorsel fin is slowly starting to deteriorate and it almost looks like another fish bit him. Any suggestions on what it is? A disease maybe? I'll try to post pics later
The tank is a 40g and the other fish in there aren't aggressive. They are cardinal tetras, rummynose tetras, and 2 small angels that haven't bothered any fish and some ottocincluses.
