Goldfish (Carassius auratus auratus) are freshwater fish in the family Cyprinidae of the order Cypriniformes, and is native to east Asia. It was one of the earliest fish to be domesticated, and is one of the most commonly kept aquarium fish.
More than a thousand years ago – long before the western world first discovered genes, hybrids and variations through selective breeding – China began domesticating, breeding and cross-breeding the Goldfish. Naturally, several distinct breeds have since been developed. Goldfish breeds vary greatly in size, body shape, fin configuration and colouration, with various combinations of white, yellow, orange, red, brown, and black known today.
While the Goldfish was originally reared as food fish, some of the normally grey or silver species had a tendency to produce red, orange or yellow colour mutations; this was first recorded in the Jin Dynasty (265–420).
During the Tang Dynasty (618–907), it became popular to raise carp in ornamental ponds and water-gardens. When a natural genetic mutation produced a gold, or yellowish orange shade rather than the normal silver, people began to breed the gold variety instead. Then, on special occasions at which guests were expected, the fish would be moved to a much smaller container for display.
By the Song Dynasty (960–1279), the domestication of goldfish was firmly established. In 1162, the empress of the Song Dynasty ordered the construction of a pond to exclusively collect the red and gold varieties. People outside the imperial family were forbidden to keep goldfish of the gold variety as yellow was the imperial colour. This may be why there are more orange than yellow goldfish still today, even though the golden variety is genetically easier to breed.
During the Ming Dynasty (1368-1644), the raising of goldfish moved indoors. This led to the selection for mutations that would not be able to survive in ponds. The occurrence of other colours apart from red and gold was first recorded in 1276. The first occurrence of fancy-tailed goldfish was recorded in the Ming Dynasty. In 1603, goldfish were introduced to Japan, where the Ryukin and Tosakin varieties were then developed. In 1611, goldfish were introduced to Portugal and from there to other parts of Europe.
During the 1620s, goldfish were highly regarded in southern Europe because of their metallic scales, and came to symbolise good luck and fortune. It then became tradition for married men to give their wives a goldfish on their one-year anniversary, as a symbol for the prosperous years to come. Eventually as goldfish became more readily available, they lost their status and the tradition died. It was only much later, in 1850, that Goldfish were first introduced to North America, where they quickly became popular.
When found in nature, goldfish are olive green. Introduction of domesticated goldfish into the wild can cause problems for native species as Goldfish can hybridize with certain other species of carp. Within three breeding generations, the vast majority of the hybrid spawn revert back to their natural olive colour. Koi may also interbreed with the goldfish, but the result is a a sterile hybrid fish.
The fancy goldfish of today are unlikely to survive in the wild because of their bright fin colours; however the hardier varieties such as the Shubunkin may survive long enough to breed with wild cousins. Common and comet goldfish can survive, and even thrive, in any climate that can support a pond.
Goldfish, if properly taken care of, can live a long time. The average lifespan of pet goldfish is 10 to 15 years. It therefore seems cruel to confine Goldfish to a small table-top bowl. Goldfish should be kept in conditions corresponding to their natural habitat, and their aquarium should allow enough room for the fish to swim freely. Goldfish, being cool water fish, grow much larger than many tropical fish you’d see in tanks. It is therefore also pointless to keep them in a too small tank.
All things being equal, a larger tank makes it easier to keep goldfish healthy, because of the larger volumes of water. A longer tank is preferable to a higher tank in order to get a better oxygen to water ratio. The larger the surface area of the water, the better the gas exchange between the air and the water. Because goldfish are cool water fish, they need more oxygen in the water than other kinds of fish. They therefore need an aerator. They also need good filtration, as they are messy eaters and, like most carp, produce a large amount of waste both in their faeces and through their gills. A build-up of these toxic wastes can occur in a relatively short period of time, and can easily cause death.
Most Goldfish hobbyists recommend larger sized gravel or even river rocks for the bottom of the aquarium – otherwise nothing at all, because goldfish like to forage for food on the bottom and can choke on smaller sized gravel.
Rapid temperature fluctuations and too low or too high a temperature can affect or harm goldfish, and in severe cases may even cause death. The optimum temperature for goldfish is between 20 and 22°C.
Because goldfish eat live plants, they are not suited to a planted aquarium. Nevertheless, if wisely decorated, a Goldfish aquarium can be really spectacular, as can be seen in the picture below. Goldfish are gregarious and will display schooling behavior when kept in a group.
In the wild, the diet of goldfish consists of crustaceans, insects, and various plant matter. Like most fish, they are opportunistic feeders and do not stop eating of their own accord. Overfeeding can be deleterious to their health, typically by blocking the intestines. This happens most often with selectively bred goldfish, which have a convoluted intestinal tract. When excess food is available, they produce more waste and faeces, partly due to incomplete protein digestion. Overfeeding can sometimes be diagnosed by observing faeces trailing from the fish’s cloaca.
Goldfish-specific food has less protein and more carbohydrate than conventional fish food. It is sold in two consistencies—flakes that float, and pellets that sink. Enthusiasts may supplement this diet with shelled peas (with outer skins removed), blanched green leafy vegetables, and bloodworms. Young goldfish benefit from the addition of brine shrimp to their diet.
Goldfish have strong associative learning abilities, as well as social learning skills. In addition, their visual acuity allows them to distinguish between individual humans. Owners may notice that fish react favorably to them, swimming to the front of the glass, swimming rapidly around the tank, and going to the surface mouthing for food – while hiding when other people approach the tank. Over time, goldfish learn to associate their owners and other humans with food, often “begging” for food whenever their owners approach.
If you wonder about the adult size of goldfish, perhaps the illustration below will give you a better idea of what to expect.
Having said that, here is an image of the current world record holder, size-wise: