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Japanese Koi

Japanese Koi are regarded as the prized fish of all the pond fish; they are sometimes called “Living Jewels”. Koi can live to be 20 to 30 years old.

Koi are believed to originate from eastern Asia and China. Koi were discovered by accident as colored genetic mutations from native black carp. The carp breed naturally, producing many thousands of offspring, some of which were not black like their parents but pale yellow. The cherished pale yellow Koi were crossed with other similarly colored genetic mutations, which eventually turned into the Koi we know and love today.

The Japanese tradition offer the best quality Koi, with deep red pigmentation and clear skin in metallic varieties. In Japanese tradition approximately only 1 percent of a typical spawning Koi reaches the market. The other 99 percent do not survive as they are not considered to have reached the optimal grade.

All Koi names are in Japanese, most of the terminology we use for pets have been translated into English. The reason why many Koi terms have been left in Japanese is because they could not be translated without creating considerable difficulties. Japanese breeders coined their terms as each variety was established, and while certain terms can easily translate, others cannot, so it was simpler to use the terms already in existence because they were very specific and a translation might change their meaning. This does not present a difficulty because in any hobby the terms used must be learned on a build-up basis.

Koi Variety

 Gin Rin Chagoi Fish picture

Japanese Koi were first bred for color in Japan in the 1820s, initially in the town of Ojiya. The outside world was not aware of the development of color variations in Japanese Koi until 1914, when the Niigata Koi were exhibited in the annual exposition in Tokyo. At that point, interest in Koi exploded throughout Japan.

The hobby of keeping Koi eventually spread worldwide. Koi are now available in a wide range of colors, and pattern variety. While there are a limited number of major Koi varieties, there are numerous sub varieties or types. To the Japanese, many of these types are considered to be of “low quality” if they lack desirable characteristics of the varietal group.

It is important not to consider the groupings synonymous with “Pedigree’s”, as this is not always the case with Koi. It is the actual physical characteristics of a given Koi that determine its classification, not its pedigree line.

Asagi and Shusui are categorized as one during competition. The Asagi or "light blue" are generally red or orange with gray or blue at the back. Their patterns are normal or doitsu. The Shusui or "autumn water" is similar with the asagi except that they come only in doitsu pattern.

The Bekko or "tortoise shell" as it resembles a turtle and comes in white, yellow or red with black patterns.

The Hikari utsuri mono comes in two colors, metallic and flat. The metallic color is bright, whether it is white, red, or black. The head is without any markings or patterns.

The Hikarimoyo mono has a metallic base. It may have markings but should have a metallic base. Or it may be two metallic colors.

The Kawari mono or "catch-all" are the Koi that cannot be put into the other categories, such as the Karasu goi that has an overall black cover.

The Kinginrin, like the Hikarimoyo mono, is also metallic. But unlike the Hikarimoyo mono, it has silver markings.

The Kohaku have a white body with orange or red markings. Ideally they should not have any markings on the fins, mouth and below and below the eyes.

The Koromo are non metallic and white-bodied. The Kohaku only has orange or red markings, the Komoro has additional black or blue markings.

Ogon are single-colored metallic Koi, usually white or silver or yellow.

Showa sanke have a black body with red and white markings.

The Taisho sanke is similar to the Kohaku except that instead of just the red markings on white body, it has additional black markings.

Tancho are Koi with a white body and the only other color is a red patch on the head.

Utsuri mono has non metallic black body with one color markings. The markings are either in red, yellow or white.


Koi are very sociable fish and will become tame and feed from your hand. They are fast growers and greedy feeders. Koi are excellent pond fish and are within everybody’s budget. Koi are very compatible with other fish, but they can out compete smaller fish at feeding time.

The higher the grade of Koi, the less hardy it will be. Japanese Koi are omnivores and will thrive on commercial dry Koi foods and readily accept moist treats such as worms, prawns, and even oranges.

Koi grow up to 3 feet in length but will reach 4 feet in a sizable pond. Water must be well filtered and circulated to provide a stable pond environment.

Don’t be put off by the high dollar Koi that are out there, those are mostly show Koi fish. It is possible to collect some very nice Koi without spending a fortune. I have yet to spend a lot of money on my fish and I have had some really astounding fish.

Ghost Koi

There are many varieties of Japanese Koi fish but the most popular are Ghost Koi and Butterfly Koi. These are not officially recognized and you will not find them in a Koi show. They have become popular with pond keepers due to their unique characteristics.

The Ghost Koi is a controversial pond fish. To the Koi purist, it is regarded as a misfit that should have been culled, but to the average pond keeper, it is one of the most desirable fish.

The most visible and striking areas of a Ghost Koi are the metallic head and flashy pectoral fins that glint in the sunlight. Ghost Koi are an excellent choice for the novice pond owner, as they are vigorous, tame, and rewarding to look after.

They are available in a wide range of sizes and shades and are very competitively priced. They have a reputation for becoming tame very quickly, endearing themselves to the pond keeper right away.

A benefit of keeping Ghost Koi is their enhanced vigor, health, and vitality they don’t require pampering to keep them in the best shape. In fact, Ghost Koi has such a high natural resistance to disease that the need to treat them for aliments is very rare.

Butterfly Koi

 butterfly koi Fish picture

Butterfly Koi has become the unconventional favorite in the U.S. Just like standard Koi, they are available in a wide range of colors. Metallic varieties are especially stunning.

The defining features are long, trailing butterfly fins and tail and a long, slender body.

Show Quality

A potential exhibition Koi should be well marked according to its variety; in the solid color varieties then the color should be dense and even over all the Koi; any hint of fading would be a bad fault. In varieties such as Kohaku and Showa, the pattern must be interesting. This is not an easy term to qualify because what is interesting to one judge may not be to another. However, it is desired that the pattern should be as even on both sides of the dorsal fin as possible. Good bold patches of hi and sumi are better than tiny spots of color, and the colors must not intrude on each other. The white of Koi should always be as pure as possible with no hint of pink or yellow.

Shape is most important to a Koi and scores more points than any other single feature: 30. Color is awarded 20 points as is the pattern. Quality earns 10 points and elegance 10 also, as does imposing appearance. These latter terms leave much room for individual thoughts.


Koi are normally judged by a team of experts which will be composed of 7-9 judges at a big Japanese show. Initially, about one third or one quarter of all entries are selected from the size and type classes and these go forward to the second stage. From this reduced number a 1st, 2nd and 3rd for each variety and each size is chosen and these become champions; others that reach this stage are awarded prizes also. At the third stage there are 1st, 2nd and 3rd prizes given tot eh winners of the 15 sizes so that there are by this stage 45 Koi left in the competition. From these, the grand champion is chosen-an extremely high honor in Japan.

Only a single grand champion is chosen at the All Nippon Show but other societies may award 2nd, 3rd and 4th grand champions behind the overall winner.


No Koi should ever be entered into an exhibition unless it is in the finest of condition. If you have an entry for your Koi, check it over before the show and if it has developed a problem or maybe a cut, a lost piece of fin due to nipping, it is better to lose your entry fee than to show such a fish just because you paid your fee. In the UK the Koi society has now introduced rules that effectively disqualify such Koi from exhibition.

Japanese Koi Fish Size

Koi Fish 8 Size System

  • Up to 18cm (7”)
  • Up to 20 cm (8”)
  • Up to 25 cm (10”)
  • Up to 30 cm (12”)
  • Up to 35 cm (14”)
  • Up to 40 cm (16”)
  • Up to 45 cm (18”)
  • Up to 50 cm (20”)
  • Up to 55 cm (22”)
  • Up to 60 cm (24”)
  • Up to 65 cm (26”)
  • Up to 70 cm (28”)
  • Up to 75 cm (30”)

15 Size System

  • Up to 15cm (6”)
  • Up to 80 cm (32”)
  • Over 80 cm (32”)
  • Up to 25 cm (9 ¾”)
  • Up to 35 cm (13 ¾”)
  • Up to 45 cm (17 ¾”)
  • Up to 55 cm (27 ½)
  • Up to 65 cm (25 ½)
  • Up to 75 cm (29 ½)
  • Over 75 cm (29 ½)

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References for Koi Variety: Knowing Your Koi by: Rob Mills

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