Goldfish originally came from China.  Goldfish differ from Koi in that goldfish grow to a maximum of about 12 inches whereas Koi will grow to more than 2 feet long.  Also, goldfish don't have barbs at their mouth.

Comets have a single tail whereas as fantails and fancy goldfish have forked tails.  Orandas have a red cap on their forehead and they have the dorsal fin typical of comets.  Ranchus have no dorsal fin and an extreme arch to their back.  Ryukins are similar to a fantail, but they have a pointed nose and tall hump on their back, which gives a notched appearance to their profile.

Scientific Name:   Carassius auratus  Family:   Cyprinid  Temperature:   0 - 38 C; 32 - 100 F  PH   7.0 - 7.5  Size:    30 cm; 12 inches  Life Span:    decades  Breeding:    Easy, Egg Layer

Goldfish are extremely hardy and can survive outdoors in freezing conditions provided that they have a fresh supply of oxygen through the ice.  They eat a variety of flake and pellet food, as well as plant material.  Breeding occurs in temperatures around 75 degrees Fahrenheit and can result in hundreds of eggs.  The fry hatch in five to six days.

Goldfish are predominantly an outdoor cold water species, but they can tolerate warm temperatures and aquarium life easily.  An aquarium of at least 30 gallons is recommended and it should be lightly stocked, as goldfish are quite messy.

The following article was submitted by "LittleHippyGirl" from our forum:

Goldfish can generally be divided into 2 categories: single-tailed and fancy. 

Single tailed goldfish are generally hardier but require more space than fancy varieties, so they are often better suited to ponds. Single tailed goldfish include commons, comets, and shubunkins. Commons and comets are very similar with the exception of the tail shape, and comets have long scissor-shaped tail fins. Both are most commonly seen in orange, bronze, white, orange and white, or red and white (also known as sarasa). Shubunkins have calico colors.

Fancy goldfish often have rounded bodies, fancy features, or both. Breeds include Orandas, Fantails, Ryunkins, Ranchus, Lionheads, Telescopes, Black Moors, Jikins, Wakins, Pearlscales, Celestials, and Bubble Eyes. Telescopes, Black Moors, Pealscales, Celestials, and Bubble Eyes generally are not good pond fish because they are more sensitive to cold and can’t compete with other types of goldfish for food very well. The other fancies do well in ponds if there are no koi and water temps are not too cold. Fancy goldfish come in all sorts of colors and patterns, with the exception of Jikins and Black Moors. Jikins are bred to be only white with red lips and fins, and Moors are black matt telescopes. Many more breeds are appearing, so keep on the look out. Also, all types of goldfish can interbreed and this results in “mutt” type goldfish.

Goldfish are incredibly messy fish that need large tanks, powerful filtration, and regular maintenance. A bowl is no home for these fish. The 1 gallon per inch of fish guideline does not apply to goldfish, even if you measure the adult size since much of their size is not in length, but in width too. A good suggested minimum for small fancy goldfish is 10 gallons each, and single tailed goldfish 15 gallons each, but bigger is always better for these fish. 

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