Hi all, I've just returned from holiday and all my fish seem happy and in good form. I have noticed one issue. My calico fantail has a hole in the tail fin. What I mean is its not like a chunk is missing from the end, the whole tail is intact, but there is a hole in the middle of one of the tail fins. Quite a largish hole like a long oblong, but the ends are intact and are the normal shape. The tank is a 40g with 3 fancies in total. There was an ever so slight whitish area on the fin before I left and that has become the hole now. I'm guessing it is a bacterial thing. I only have melafix to hand. Shall I go ahead and dose that? Or do you think a good water change would suffice?