I am a new member I would like some help with my fish problem. I have an assortment of tropical fish. I have three large Red Tail Sharks. I noticed on has a Ulcer type wound on its back. I have removed it into a 20 lt tank and added a heater it heat the water to 24c . I added a Table Spoon of Aquarium Salt and a does of Stress Coat. It has been in the small tank for two day but it does not seem to be improving. Please could somebody tell me what I need to do to heal the ulcer. I took a photo but it is not too clear.