The goldfish that we see today are an interesting mixture of normal forms, accidents in natures, and the science of man. Nature created the original goldfish, the Carassius auratus, from which the many varieties of goldfish today have been derived.
These fish tend to catch mutilations and this is where humans come into play. The Chinese, Japanese, and Koreans take these mutations and create exaggerations, developing them over centuries. These developments have created the various colors and types of fish, like enlarged fins or bulging eyes.
Goldfish came from China originally, and this culture is the first to have bred and developed the fish.
There is a Chinese fairytale from around 700 years B.C. talk about a goldfish that jumped out of a well, and brought back the rain after a long drought.
Goldfish, being kept as pets, dates back to the tenth century AD during the Sung Dynasty. There are references to breeders who were able to change the color of their fish. After the thirteenth century, there were red, gold, black, and mottled colored fish that were easy to find and keep as pets. These fish have become a constant part of Chinese society. Japan also kept these fish as pets in 1500AD, but they were not cultivated or bred until over 200 years later.