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Which Koi Types Grow the Biggest?

Which Koi Types Grow The Biggest?

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Koi are popular ornamental fish to raise in a home pond. Besides mere appeal, koi’s potential to grow up to 30 inches long makes them valuable centerpieces for any backyard. Big Girl, the largest recorded koi fish in the world (48 inches long), whose owner has no plans of selling, but would take nothing short of $40,000 if ever. This may make you wonder which types of koi would come close to that size. Begging the question, which koi types grow the biggest?

Jumbo koi are the largest koi type. This is a colloquial term for koi fish that can grow at least 30 inches long. In reality, there are over 100 specific types of koi that koi farmers can selectively breed to produce “Jumbo” koi. This article highlights different koi types, how large they can grow, and the ideal environment for koi to grow to their largest potential size.

How Big Can Koi Fish Grow?

How Big Can Koi Fish Grow

Since there are over a hundred types of koi fish, many breeders use four colloquial terms to classify koi fish: domestic, imported, Japanese, and jumbo. Other experienced breeders are more specific with their koi classifications and identify nine groups of koi, which break further down into subgroups based on their Japanese variety.

Domestic Koi

Koi farmers breed domestic koi in the U.S. This koi type usually grows between 12 to 15 inches long. Domestic koi have the least growth rate among the four standard varieties. These koi fish can be more manageable to raise in a home pond over the larger varieties that competitive breeders or professional koi farmers raise for themselves.

Imported and Japanese Koi

Imported koi are the type that koi distributors bring in from other countries into the U.S. This koi type is separate from Japanese koi to highlight the fact that koi that come from Japan are different from imported koi. Other countries that import koi fish include India and China. Even if U.S. distributors import koi from these countries, claiming they are Japanese koi, they wouldn’t be considered Japanese koi because they did not come directly from Japan.

Japanese koi usually grow up to 22 to 26 inches long. These brightly colored large fish can weigh up to 12 pounds, with healthy ones weighing up to 24 pounds. This koi type comes from selective breeding, allowing them to reach such large sizes. If you intend to raise Japanese koi, be sure you can accommodate their large size and maintain their proper diet. Japanese koi farms raise koi with intensive care to ensure they reach the largest possible size.

Jumbo Koi

Jumbo koi types grow the biggest among the four colloquial categories. These fish can grow between 30 and 36 inches long. With proper care and diet, some koi can grow up to 40 inches long. Jumbo koi can weigh anywhere between 20 and 26 pounds. Like Japanese koi that grow large, Jumbo koi require intensive care to reach their full potential.

Jumbo koi genetics is the main factor that gets these fish to reach such sizes. Koi farmers selectively breed their jumbo koi fish and do not reveal their trade secrets. After all, large koi can be considered living jewels. Jumbo koi would not be as valuable as they are if every koi breeder knew how to produce high-quality koi fish.

How To Raise Koi To Grow Big

How To Raise Koi To Grow Big

Raising koi to help them achieve their largest size requires intensive care. Whether your koi fish are domestic, imported, Japanese, or jumbo types, an ideal environment will help them grow to their fullest potential size.

Note that genetics is the main factor that indicates how big a koi fish will grow. Even if you have an optimal pond for koi fish, a domestic koi fish will not grow as large as selectively bred Japanese or jumbo koi fish.

Here are the main factors that influence your koi’s growth:

Pond Size

Large fish require a large pond. Standard koi ponds should be at least three feet deep with 1,000 gallons of water. Each koi fish should have 250 gallons for itself, meaning a standard koi pond can hold four koi fish.

Consider your entire pond’s area instead of just its depth. Wider ponds allow koi fish more space to swim, which can be ideal for their exercise because koi are active fish. Having enough room to swim means they have enough room to grow.

Water Quality

Water pH levels and temperature are factors that contribute to a pond’s water chemistry. Koi fish prefer water with a 7.5 pH level because they tend to like slightly alkaline waters. Meanwhile, koi fish are known for being hardy and can thrive in water temperatures ranging between 59°F (13°C) and 77°F (25°C).

Still, an ideal pond temperature is around 62°F (17°C) to keep your koi fish active while making sure no parasites thrive in cold waters. Consider investing in a pond heater to maintain an ideal water temperature for your pond, especially during the cold months.


Be sure to feed your koi fish only the best quality feed to ensure they grow up big and healthy. Feeding is essential in a koi’s early stages, so make sure your koi food has all the necessary nutritional ingredients while your koi fish are young. Consider preparing a feeding schedule where you feed them at least six times a day at regular intervals.

Conclusion: Which Koi Types Grow the Biggest?

Koi fish are known for their bright colors and large sizes. Jumbo koi are the largest koi types that can grow up to 30 inches long with the right breeding conditions. You will need to provide an optimal environment to allow your koi to reach such sizes.

However, regardless of how ideal your pond is for koi, genetics is the main factor that dictates how big they grow. Koi farmers specifically breed jumbo koi to reach large sizes, so other types of koi cannot grow as large as them because they were built that way.

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