...the cause of his death? I had my fish for nine years. If this bump did kill him, what is it called?
He was a fancy tail goldfish. He lived in an aquarium filled with water from the facuet. I had him for 9 years.
Need more info what kind of fish would be helpful, what's water cond. ph and so on, some fish naturally can have a bump on head some species it is a sign of maturity