Hello, So I have this Hamanashiki GoldFish (a Pearl one) and, from one day to another, a big bruise on his side appeared. At first I thought it was just a bruise but it has started to get redder everyday. A friend of mine recommended me to put Blue Methylene directly on that side just in case it was a kind of fungus so I did and something that looked like cotton falled down. Neverthless, it didn't do much for the bruise (I did it twice). I started to read about it and there was some people that said it is a bacteria and that is probably an ulcer so I looked for it online and it is not as bad as those pictures. The fish looks completely healthy and normal. He swims normally, eats normally, behaves normally... it's just that bruise alike stain that it has that's bothering me. Parameters: Ph: 7.5 Nitrates and Nitrites = 0 Tank Size = 200 liters (I have 4 big Goldfishes) Cannister Sera 1100 2 oxygen difusors stones Every help will me much appreaciate it. Thanks you in advance.