If the fish was acting normal then I'd say it is type of goldfish who naturally has a bubble on it's head and it's quite possible that the fish was so young as to not yet develop a noticeable bubble. However, thinning fins and sitting on the bottom isn't a good sign for a goldfish.
I'm afraid I can only provide a very vague answer. Your fish is probably ill. If you're really attached to the little guy or gal, I suggest taking it to a vet and getting their opinions on it.
I'm afraid I can only provide a very vague answer. Your fish is probably ill. If you're really attached to the little guy or gal, I suggest taking it to a vet and getting their opinions on it.
