I have a newly bought fantail goldfish that is black white and orange and on him just before the tail there is a small white lump, it looks to me to be a birth defect but i think theres a possiblity it could be a fungus? i dont think it looks really cotton-like but as i have had an experience with fungus causing the death of my fish before now and i wondered if there was anything to help me diagnose this better?
the conditions in my tank are as follows :
ph : 6.4
nitrate : 0
nitrite : 0
food : flake food & weekly freeze-dried food cubes
there are no other unusual markings occuring on this fish and his behaviour is normal
and he is only a recent purchase though.