Noticed yesterday that my Gold Piranha had developed some sort of "ulcer" or abrasion on his side. The tank is sparse with nothing rough or sharp that he may have injured himself on. The only thing I can think of is he nesstled up to the heater and somehoe burned himself??? Any suggestions would be appretiated and any help on how to medicate if even possible. Heres a (not so great) pic of the "ulcer" for lack of knowing what it truly is. The fish is the lone inhabitant in its tank so a bite is out of the question.