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Koi Fish Species

A Beginners Guide To Koi Fish Species

Koi fish species scientifically speaking, are species of a Carp. However, is often referred to as “Nishiki Koi”, which is Japanese for Brocaded Carp. Although outwardly very similar in body form to Common Goldfish, Koi grow much large and have a single barbel at each corner of the mouth.

Koi have traditionally been cultured to be seen from above – that is, as they swim in a pool. This is due to the way they are kept in their country of origin, Japan, where garden pools are extremely popular.

Koi Species Comparison

Koi Fish SpeciesColorsEase Of Keeping
Kohaku & HariwakiRed, Gold, White & SilverEasy
Asagi & TaishoLight Blue, White, Orange & BlackEasy
Mongrel Yellow Or OrangeVery Easy

Koi fishes are divided into single-color, two-color and multi-colored varieties, and are further distinguished by their scale development. Some do have a few large scales, whilst others may have pine-coned effect, and a third group have extra metallic speckling.

You’ll soon discover that prize-winning specimens may be one metre long and can cost several thousand dollars. These Koi fishes can’t not be produced and grow in an aquarium; only juvenile forms should really be kept indoors.

Japanese Koi Fish Species

Once Koi grow around 4.5 inches long, they should really be moved to outdoors to larger, natural living quarters. However, if the pond is likely to freeze over in the winter months, a minimum water depth of at least 5.0 feet must be provided for safe overwintering.

One factors to bear in mind, is that Koi fishes will breed quite readily in a pond. Some keepers and hobbyists find it better to collect their eggs after spawning and hatch them in an indoor aquarium, as conditions fluctuate less often.

Species Of Koi Fish


Kohaku & Hariwaki Koi (Two-Color Koi)

Kohaku Koi Fish

The white variety with red markings is a Kohaku, whilst the fish with gold and silver patterning is a Hariwaki. Both have the typical carp-shaped body, with the greatest depth occurring just forward of the long-based dorsal fin.

Also, their down-turned mouths show that they are bottom feeders, but they will also eat floating pellet foods.

Kohaku & Hariwaki – Species Details

  • Size: Up to 9.8 inches
  • Origin: Japan
  • Sexing: Males have breeding tubercles on pectoral fins; females are fatter.
  • Ease Of Keeping: Very easy
  • Food: All varieties
  • Breeding Method: Egg scatterer
  • Breeding Potential: Easy

Kohaku & Hariwaki – Aquarium Conditions

  • Water: All types, although has to be well-filtered.
  • Temperature: 0°C – 20°C
  • Tank Type: Species
  • Swimming Level: All levels

Asagi & Taisho Sanke Koi (Three-Color Koi)

Asagi Koi Species

A Koi fish of the Asagi species tends to have a light-blue body marked in orange and black, and Doitsu scales. Taisho Sanke have the traditional three colors of red and black on white skin.

Asagi & Taisho Koi – Species Details

  • Size: Up to 9.8 inches
  • Origin: Japan
  • Sexing: Males have breeding tubercles on pectoral fins; females are fatter.
  • Ease Of Keeping: Easy
  • Food: All foods
  • Breeding Method: Egg scatterer
  • Breeding Potential: Easy

Asagi & Taisho Koi – Aquarium Conditions

  • Water: All types, although has to be well-filtered.
  • Temperature: 0°C – 20°C
  • Tank Type: Species
  • Swimming Level: All levels
  • Special Needs: Space

Mongrel Koi

Mongrel Koi Fish

These tend to be either yellow or orange fishes that do not fit into any color standards recognized by specialist Koi keepers or societies. It can therefor be entered for showing, but this doesn’t mean that it will not make an attractive addition into your pond.

Another aspect to mention is that they tend to be cheaper in comparison to the other two species previously mentioned, as they’re not regarded as ‘show-quailty’.

Mongrel Koi – Species Details

  • Size: Up to 9.8 inches
  • Origin: Japan
  • Sexing: Males have breeding tubercles on pectoral fins; females are fatter.
  • Ease Of Keeping: Easy
  • Food: Most foods
  • Breeding Method: Egg scatterer
  • Breeding Potential: Easy

Mongrel Koi – Aquarium Conditions

  • Water: All types, although has to be well-filtered.
  • Temperature: 0°C – 20°C
  • Tank Type: Species
  • Swimming Level: All levels
  • Special Needs: Space

Koi Fish Pond Conditions

Out in the wild, a Koi fishes counterpart is the Common Carp fish, which is native to Asia and Europe. Their environments tend to be ponds, lakes and streams, that have minimal flow.

School Of Koi Fish

In addition to that, they are found in both temperate extremes and tropical areas. But, they prefer temperatures of at least 70°F and above.

They  are mostly active in dimly-lit hours, which are dusk and dawn, but you can find them swimming and foraging through all hours of the day. Creating these conditions in your own pond or environment is not a difficult task.

What Size Pond Do Koi Fishes Need?

Koi fishes require a size pond of at least 250 gallons water, that is then increased when you have a school of Koi which need 100 gallons! Moreover your pond should should have a minimum depth of at least 6 feet, among having deeper and shallower areas of the pond.

Koi Fish Pond

There is a rule that many hobbyists follow, which is you should have 10 gallons of water per 1 inch of your fully grown Koi fish. This means one Koi requires at least 250 gallons of water.

What Do Koi Fish Eat?

Koi fish are Omnivores, which means that they’ll eat seeds, plants, algae, insects and Plankton. Though they may not eat other fish, you may find that they’ll eat their eggs.

If you wish to provide them with a well-balanced diet, then you should have a good mix of veggies and critters for them to feed on. Check out our article here of the best commercial Koi foods.

What Do Koi Fish Eat

Commercial Koi foods are great, as they will be high in protein for growth and development, plus they will feed on all levels of the pond. You should feed your Koi up to 3 small portions or 2 large portions of food a day.

Conclusion

Ultimately Koi Fishes are great outdoor fishes to keep. They’ll bring vibrant life into your outdoor aquatic environments, plus they’re easy to keep and get along with many other aquatic creatures. Hopefully if you’ve gone through our beginners guide, you would’ve learnt a bit about the various species of Koi and some tips on keeping them!

About The Author

the aqua guru author

Jon is an aquarium keeper of over 15 years and the owner of Guppy's, Betta's and other marine life. He always likes to make changes to his aquarium for the benefit of his marine life's well-being and health using the best aquatic products on the market. You can read more about us here.