How Big Do Koi Fish Get?


Koi fish lengthen 20-24 inches and weigh 9-12 pounds on average. These numbers are even much more, which makes you shout loud.

People might have been wondering about their size, growth speed, etc. In “How big do Koi get?”, you will get knowledge about the size of koi varieties, many factors affecting their growth.

Also see: Best koi pond filter

How Big Do Koi Fish Get – In General

Originally, Koi fish were caught by Japanese cultivators then, selected to breed and create the nowadays koi fish, whose colours are like stunning Amur Carp.

Suppose you like keeping this fish in your indoor tank, you need to know detailed information about how big koi fish grow. Mature Koi fish probably develop up to 36 inches long on average. Their growth ratio is 0.8-0.9 inches a month; however, this rate depends on your own Koi varieties.

The body structure of this ornamental carp breed is similar. But depending on different patterns and colours, we can classify more than 100 various kinds of koi fish.

How Big Do Koi Fish Get – In Details

Nowadays, people typically tend to buy these big kinds of domesticated fish, but their size is too large to be kept in a tank. Otherwise, your house will become a fish tank. It is ideal for keeping your Koi in indoor ponds or outdoor ones.

The growth of a common Koi fish is around 12-15 inches. This quite small Koi breed is most suitable for these indoor tanks. In addition, there is also another Japanese small breed of Koi fish lengthening 22-26 inches. These Koi varieties can not be raised in house tanks.

Jumbo is another member in the Koi fish family, whose length is 36 inches – 3 feet, with the maximum, up to 52 inches. This size breaks the world record. Housing this fish breed outside ponds is the best way.

How Fast Do Koi Fish Grow?

Generally, it will take an average of 3 years for most Koi fish to exhibit to maximum length, but the smaller breeds will take less time to reach full length.

Jumbo Koi & the Japanese breed are not an exceptional situation. Your Koi should lengthen about 8 inches on average at the end of the first living year, and the rest will develop over the next few years.

What Are The Factors That Influence A Koi Fish’s Growing Speed?

The growth rate of Koi fish is generally the same in the initial year. There are many factors such as the daily diet quality and the parameters of water determining their development speed.

Following are the major factors impacting the growth speed of a fish koi:

  • Water temperature

75-80°F is an optimal range of temperature for Koi fish to metabolize and grow faster. The temperature factor is a major reason why Koi fish varieties are bred and kept in the West, growing faster than in Japan.

  • Stress

Koi is one of the strong freshwater fish having the resilient ability in a poor environment. However, their extreme stress sometimes can cause easy vulnerability.

The developing process may even slow down in a short time if your Koi are infected by KHV, parasite attack, or other diseases.

  • Food

The nature of Koi is omnivores so that they can eat everything. It is simple to train these fish to feed by our hands because of greedy food habits. They can do everything to become the first eater.

Koi’s development will stagnate if you do not provide enough nutrition or just a simple daily menu.

  • Overcrowding

Overcrowded koi fish can cause many bad effects, one of which is slowing down their growth speed. Another noteworthy impact is even killing a few of Koi some the first few days.

Actually, not enough space for Koi fish to live can cause serious effects on their development because this circumstance makes them strongly stressed.

Make certain that you have the ability to meet these size requirements needed for a pond or an aquarium if you desire to have a funny swarm of Koi fish in your house.

  • Age

The Koi’s growth is dependent on age, which happens fast in the first few years, then slows down and finally remains at the same speed after a certain time.

If a koi fish can not grow as well as possible during the first stage, its size will not be big after that. Therefore, full care is necessary for Koi fish to grow fast since their birth.

Nutrition, Quality, and Type of food

Nutrition plays an important role in Koi’s initial stage, especially when they are young in the strong development stage.

The daily diet should include all the essential ingredients if Koi fish eat fully many times per day so the nutrient and digestion absorption will occur well. The quick growth is obvious.

Read more: Best Koi Food

What is The Biggest Recorded Koi Fish?

The largest Koi fish named “Big Girl” is recorded in world history. Her weight is 90 pounds, reported in 2007.

“Bad Girl” was three times bigger than all mature Koi fish until now. Even there is no fish, whose weight is close to its.

A person who bought it from a breeder in Japan after it has lived for 17 years with 10 inches in length. Her size is two times heavier than a common Koi.


We know that you are finding out the necessary information to ensure that your Koi fish can reach as big as possible in size. Provided that you provide your Koi with proper food, enough space, and an ideal environment.

Hopefully, after reading through “How big do Koi get?”, your Koi can be large and healthy. Thank you for reading!

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