Goldfish are very popular pets. Some of their popularity stems from the fact that they are relatively easy to keep and very cheap to acquire. Not so many years ago, the goldfish was a prize frequently given away at state and county fairs. Still, just because these fish are plentiful, that doesn't make them common. The history of the humble goldfish is bound up with the history of emperors.
The Asian carp, from which the goldfish is descended, was kept as a food fish by the ancient Chinese. During the Jin Dynasty (265 - 420 CE), people began noticing that some of these normally gray or silver fish had mutations causing red, orange, or yellow coloration. Soon, the Chinese were breeding fish especially for their color.
By the time of the Tang Dynasty (618 - 907), it was popular to keep these ornamental fish in home ponds. When guests were expected, the well-to-do would even put their prettiest fish in containers to be brought inside for display.
It is known that an empress of the Song Dynasty (960 - 1279) kept just such an ornamental pond herself. During this time, people outside of the royal family were forbidden to keep yellow goldfish, as yellow was the imperial color. Commoners could keep orange goldfish, so these were bred en masse and are still the most common color variety today.
During the Ming Dynasty, goldfish bagan to be raised in indoor aquariums. This allowed for the breeding of varieties too delicate to survive outdoors. During this time, fancy-tailed goldfish began to appear.
Goldfish were introduced to Japan in 1603, to Europe in 1611, and to North America in 1850. Today, there are around 50 varieties and goldfish are one of the most commonly kept aquarium fish.