fish are very resilent critters tougher than we give them credit for. A uv serilizer will kill bad bacteria that may inhibit the healing process also and I did say put it inthe sump maybe the return line would be better that way all the water has to pass through it to get back in to the tank. anyways as I sugested before melifix would aid in the healing process for the skin and scails any ways. It may help sooth the sun burn that theu got I don't know about soothing but it does sound good.

Good luck again and I hope all other s pull through and keep your chin up..

Bill