Goldfish, Carassius auratus, are domesticated freshwater fish descended from wild carp. Their long history in aquariums and ponds has produced many varieties, from streamlined common goldfish to round-bodied fancies with flowing fins. They are popular for good reason. Goldfish are active, visible during the day, and full of personality. Many learn where food appears, respond to the person who feeds them, and investigate changes in their environment.