The common goldfish (Carassius auratus auratus) is one of the oldest domesticated fish, bred around 1000 years ago in China from the Prussian or gibel carp (Carrasius gibelio). Artificial selection since then has created over a hundred varieties of goldfish with diverse colors, sizes, body shapes, and fin, tail and eye characteristics. Goldfish are a popular aquarium fish, stock for ornamental pools, bait, research animals, feeder fish for other pets, and occasionally eaten. Wild goldfish (other C. auratus subspecies) are greenish color, omnivorous, live in slow-moving waters, and are hardy, even in non-native or slightly poluted/turbid environments. Wild type and common goldfish subspecies have been introduced throughout the world, both intentionally and unintentionally, and in some places negatively impact their environment by competing with and preying on native species, causing increased incidence of algal blooms, and increasing water turbidity.

(Komiyama et al. 2009; Rowe 2010; Street 2002; Wikipedia February 3 2012 ; Wikipedia January 31 2012