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The goldfish was one of the earliest fish to be domesticated, and is still one of the most commonly kept aquarium fish. A relatively small member of the carp family (which also includes the koi carp and the crucian carp), the goldfish is a domesticated version of a dark-gray/olive/brown carp native to east Asia (first domesticated in China) that was introduced to Europe in the late 17th century. It may grow to a maximum length of 23 inches (59 cm) and a maximum weight of 6.6 pounds (3.0 kg), although this is rare; most individual goldfish grow to under half this size. In optimal conditions, goldfish may live more than 20 years (the world record is 49 years); however, most household goldfish will only live six to eight years because owners keep them in tanks under the ideal size of 10 U.S. gallons (37.85 L).


 


During the Tang Dynasty, it was popular for Chinese ponds to have carp. As the result of a genetic mutation one of these carp displayed "gold" (actually yellowish orange) rather than silver coloration. This mutation is associated with a dominant gene which also makes the breeding of this trait rather easy. The gold strain became popular for keeping in containers. Afterwards, the people began to breed the gold variety instead of the silver variety, and began to keep them in small containers to watch.

In 1162, the empress ordered the building of a pond to collect the red and gold variety of those carp. By this time, people outside the royal family were forbidden to keep goldfish of the gold (yellow) variety. An order was given to the keepers to kill all fish that were yellow in color because it offended the court, since this itself was the royal color. This probably is the reason of why there are more orange goldfish than yellow goldfish, even though it is genetically easier to breed yellow.

Since they were bred in captivity, more mutations occurred, which produced more colors. As a result, fancier varieties of goldfish appeared. According to old books and records, the occurrence of other colors were 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, they were introduced to other parts of Europe. Goldfish were first introduced to North America in 1874 and quickly became popular in the United States.


Goldfish natively live in ponds, and other slow or still moving bodies of water in depths up to 20 m (65 ft). Their native climate is subtropical and they live in freshwater with a 6.0–8.0 pH, a water hardness of 5.0–19.0 dGH, and a temperature range of 40 to 106 °F (4 to 41 °C) although they will not survive long at the higher temperatures. Indeed, they are considered ill-suited even to live in a heated tropical fish tank, as they are used to the greater amount of oxygen in unheated tanks as well as the heat burns them. When found in nature, the goldfish are actually an olive green color, and will return to this color if domesticated and then released.

In the wild, the diet consists of crustaceans, insects, and various plant matter.

While it is true that goldfish can survive in a fairly wide temperature range, the optimal range for indoor fish is 68 to 75 °F (20 to 23 °C). Pet goldfish, as with many other fish, will usually eat more food than it needs if given, which can lead to fatal intestinal blockage. They are omnivorous and do best with a wide variety of fresh vegetables and fruit to supplement a flake or pellet diet staple.

Sudden changes in water temperature can be fatal to any fish, including the goldfish. When transferring a store-bought goldfish to a pond or a tank, the temperature in the storage container should be equalized by leaving it in the destination container for at least 20 minutes before releasing the goldfish. In addition, some temperature changes might simply be too great for even the hardy goldfish to adjust to. For example, buying a goldfish in a store, where the water might be 70 °F (approximately 21 °C), and hoping to release it into your garden pond at 40 °F (4 °C) will probably result in the death of the goldfish, even if you use the slow immersion method just described. A goldfish will need a lot more time, perhaps days or weeks, to adjust to such a different temperature.

Because the goldfish likes to eat live plants, keeping it with plants in an aquarium can be quite a problem. Only a few of the aquarium plant species can survive in a tank with goldfishes, for example Cryptocoryne and Anubias species, but they require special attention so that they are not uprooted.

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 Kingdom: Animalia

 Phylum: Chordata

 Class: Actinopterygii

 Order: Cypriniformes

 Family: Cyprinidae

 Genus: Carassius

 Species: Auratus


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