My GSP has, and has had for as long as I have owned him, a yellow spot on his side/belly. I inquired about it before and it was concluded that it was either parasites or a bite mark, but he has been solitary for months as well as being treated for parasites (he wasn't eating well) and it hasn't cleared up (although he is doing great and eating fine now). Are "birthmarks" or abnormal coloration spots normal in fish? You can kind of see it in the attached image.
