Over 1,000 years ago, the Chinese were breeding carp and goldfish for bright colors and interesting body shapes. Apparently, it started as fish farming for food, but as individuals with interesting colors appeared, those were selectively bred for increasingly vibrant colors. Chinese nobility had special ponds built in their courtyards for these special fish.
In the early 1600s, goldfish keeping was introduced to Japan and Europe, where the hobby quickly became popular. Goldfish keeping was introduced into North America in the mid-1800s. Today, of course, many people enjoy having outdoor fish ponds and indoor aquaria, and this supports a pet store trade as well as a subset of the landscaping industry.
Goldfish used in outdoor ponds tend to be the plainer, hardier types, while goldfish in aquariums may be quite fancy, with butterfly or veil tails, egg-shaped bodies, telescoping or bubble eyes, inflated bubble-like tissues on the top of the head, and so on. Several fancy varieties lack the dorsal fin entirely. In east Asian countries and internationally, goldfish breeding is taken very seriously, with breed guidelines, major shows and competitions, and awards for spectacular individual specimens.
Beginning aquarists soon learn that goldfish are quite different from the other fish at the pet store, almost all of which are from tropical regions. Goldfish, however, are “coldwater fish,” native to temperate, not tropical climates. Their preferred temperature is 68 to 72 F — lower than the temperatures needed for tropical fish. Because of several water chemistry factors and their own coldwater metabolism, goldfish are one of the worst kinds of pet fish to keep in a “fishbowl” or any other small aquarium.
Goldfish farming has been an industry in Missouri, with most of the goldfish produced being sold as bait fish to anglers, or “feeder fish” sold in pet stores as food for large, piscivorous (fish-eating) fish. Along these lines, carnivals sometimes give away bagged goldfishes as prizes.
Because they can be kept in captivity, goldfish have been studied quite a bit by scientists. Much is known about their behavior; how they sense their environment through vision and hearing; how they think; and how they interact with each other and reproduce.