Hey all. We have had our tank for about 3 weeks. It’s a coral tank and they are very healthy. We acquired the tank on a rehoming basis so the corals are relatively mature. It originally had a small damsel that proved aggressive so had to rehome it after it attacked out clownfish incessantly. It wounded the clownfish and an abscess began developing. It is getting worse and not better. See the photo. It was small originally and grew to the point where the fish cannot really use its back tail fin. Any thoughts and suggestions??? We were told it would probably go away but is obviously very concerning.