Koi are a type of carp Cyprinus carpio that are bred for their distinctive colorations and patterns. Some authorities believe that Koi originated in Persia and were introduced throughout the ancient world by traders moving to or from the Middle East. The fossils of carp have been discovered in South China about 20 million years ago.

In Japanese they are known as nishikigoi which means 'brocaded' carp. They were first described in a Chinese book that dates back to the Western Chin Dynasty, 265-316 A.D. and were described as white, red, black and blue. 

Colorations

Koi are bred in every country of the world and are considered to be the most popular fish for ornamental ponds. And, no wonder. Their colorations are so lovely that they are sometimes referred to as "living jewels" or "swimming flowers".

Typically, the coloration of koi includes several colors, white, orange, yellow, gray-blue and black. The bluish color occurs because of black coloration underneath the skin. There are infinite color combinations possible, but there are certain patterns which are considered most desirable, for example, a round patch on the forehead and a stepping stone pattern down the back. Sometimes a diamond design is created by missing scales.

Koi breeders have named a number of varieties of koi based on their patterns. There is a great deal of secrecy among breeders because the breeding process is quite involved and many varieties are not easily bred. Hence, much of the knowledge about how to breed koi for certain characteristics is not well known. Some koi with rare and desirable markings can cost hundreds or even thousands of dollars.

Keeping Koi

Koi are a very hardy fish and can be kept in ponds and containers of various sizes. However, they grow very quickly and soon outgrow small tubs. They do much better in a pond that is at least half a meter deep. Koi are cold water fish, so if you live in a place where the summers get very warm, you'll need to have a fairly deep pond.   

Because koi are so brightly colored they are an easy mark for predators. Herons, kingfishers, raccoons, cats, and foxes can clean out a pond overnight. One way to keep herons away from koi is to be sure that the pond is too deep for herons to stand in. Savvy pond owners also create overhangs that are high enough above the water so that raccoons can't reach in and help themselves.  However, in the end it may be necessary to place netting over the pond to protect the koi from predation.

Koi are herbivorous and eat vegetation. In fact, if you may have noticed that most koi ponds are devoid of any plant material. Koi can be voracious eaters and are not usually compatible with plants in a garden pond. They devour water plants. Because koi are bottom feeders, most koi owners feed their fish commercial food pellets that float to encourage them to come to the surface. Koi can become very tame, even to the point that they can be trained to eat from your hands.

Koi Varieties

There are many different varieties of Koi. Here is a list of some of the more popular ones: 

	Asagi - light blue on top, red/orange on bottom, blue scales bordered in white
	Bekko - primary color red/orange/yellow/white, with black patches
	Goshiki - mostly black, with red, white, brown, and blue accents
	Hikari utsuri mono - two metallic colors
	Hikarimoyo mono - two colors; one flat, one metallic
	Kawari mono - miscellaneous
	Kinginrin - bright metallic sheen, silver highlights
	Kohaku - red accents on white body
	Koromo - red and white overlaid with blue or silver
	Ogon - uniform yellow or white
	Platinum ogon - pure white
	Showa sanke - black with red and white markings
	Shusui - similar to asagi, but with large scales in a dorsal row
	Taisho sanke - primarily white, with red and black markings
	Tancho - primarily white, with a red patch on the forehead
	Tancho kohaku - pure white, round red head patch
	Utsuri mono - uniformly black, with red, white, and yellow markings