Goldfish are NOT the same species as common carp... Goldfish are the human genetically selected species from the parental species of Prussian carp. Koi are the same as common carp, just with fancy fins and colors.
Goldfish reach maximum size of about 16" with 10" being large. My experience is goldfish are usually removed in short order when bass or walleye are added... Carp, that is another thing altogether.
