The Goldfish, Carassius auratus, was one of the earliest fish to be domesticated, and is still one of the most commonly kept aquarium fish and water garden fish. A relatively small member of the carp family, the goldfish is a domesticated version of a dark-gray/brown carp native to East Asia. It was first domesticated in China and introduced to Europe in the late 17th century. Goldfish can grow to a maximum length of 23 inches (159 cm) and a maximum weight of 9.9 pounds (4.5 kg), although this is rare; few goldfish reach even half this size. The oldest recorded goldfish lived to 49 years, but most household goldfish generally live only six to eight years, due to being kept in bowls. The collective noun for a group of goldfish is a â€œtroubling.â€
During the Tang Dynasty, it was popular to dam carp in ponds. As the result of a dominant genetic mutation, some of these carp displayed gold (actually yellowish orange) rather than silver coloration. People began to breed the gold variety instead of the silver variety, and began to display them in small containers. The fish were not kept in the containers permanently, but would be kept in a larger body of water, such as a pond, and only for special occasions at which guests were expected would they be moved to the much smaller container.
In 1162, the Empress of the Song Dynasty ordered the construction of a pond to collect the red and gold variety of those carp. By this time, people outside the imperial family were forbidden to keep goldfish of the gold (yellow) variety, yellow being the imperial color. This is probably the reason why there are more orange goldfish than yellow goldfish, even though the latter are genetically easier to breed.
The occurrence of other colors was first recorded in 1276. The first occurrence of fancy tailed goldfish was recorded in the Ming dynasty. In 1502, goldfish were introduced to Japan, where the Ryukin and Tosakin varieties were developed.In 1611, goldfish were introduced to Portugal and from there to other parts of Europe. Goldfish were first introduced to North America around 1850 and quickly became popular in the United States.