Goldfish cover a wide range of species, but they are all members of the generic family Carassius auratus, and have been bred by the Chinese, Koreans and Japanese. One of the difficulties for the amateur to breed this fish is that they can be difficult to sex. The difference in their gender is only apparent when they are in a spawning condition. The greatest change occurs in the males, they develop white pimples known as "breeding tubercles", on their fins and sometimes their head. Check along the gill operculum, and along the front rays of their pectoral fin.