Hey
I got a lionhead the other day to add to my goldfish tank and it seems happy as like the other goldfish but the other day i noticed something green clinging to its head. I have a photo of it although its hard to see what it is, I have tried brushing it off lightly with my hand which did nothing. So i was just wondering if this is some sort of parasite on the fish or if its a natural growth, its hard to see clearyl but it almost looks like a bug of some sort.
If you got any idea what it is and if its harmful or not please let me know, although the fish seems happy and still eats and swims around and so on.

Thanks for the help

Could it be hole in the head? I was studying some symptoms for this disease, but I am very sorry to say that I can't remember what else to look for for now... I only know that there should be pus coming out of the wen like this, almost looking like a worm. For now, I hope someone else will help! It's gonna take a while before I can get to my books to find a proper diagnose and treatment... :'D