Not sure what’s wrong with my fish. Got this fish about 3 years ago. Always been fine, in a small tank. Moved him in to a 50 gallon tank, and randomly( few months in ) grows a big ball on his head looks weird looks like 50 small little bubbles. Not sure what’s wrong I feed him pebbles and used to feed him flakes I change/clean tank every few ( 2-3 ) months ( water always looks good ) can anyone help me out? Not sure if he’s in danger or pain. ( I tried to link a picture but didn’t let me)
From the description you're giving, I suspect your fish is a Ranchu goldfish, a breed of goldfish known for it's bumpy head produced by extensive selective breeding.
I believe the specific term is lymphosystist, a genetic disorder characterized by an extremely lumpy head, present in Ranchu breeds.
How do you get lymphosystist? your family tree must be a straight line, or, in other words, inbred as hell.
It may affect your fish's ability to breathe and may make him more susceptible to infections