I've had my angelfish for about 2 years and a few months ago I put in a gourami with him. I saw the angelfish nudging him away a few times when he came too close and after a while the gourami had a tiny wound on him which I thought was due to this and I thought it would heal but it got bigger and the fish died. Now my angelfish has it!! Is it an infection? and can I stop it from killing him?