Amazing Growth Rates of Koi

by Aquatics on November 11, 2011

Koi Fish Pond

Did you know that koi fish are indiscriminate growers? This means that they continue to grow all their lives. Just like humans, the fastest growth rate is in the earlier years. I just measured my 6-year-old daughter with a pencil mark on the closet door. She grew 2 inches in 12 months! That is pretty fast.

Consider koi when they hatch weigh just milligrams and can attain an adult size of 40 pounds (18 Kilograms) in ten years. That is an increase of 360,000 times. This would be like my 8-pound baby girl growing to 2,880,000 pounds in 10 years. That’s amazing.

Koi Food

Optimum growth rates in koi can be obtained when water temperatures are 74-78 degrees. Food will be the main factor along with maintaining great water quality. Ensuring that there is a continuous availability of food via hand feeding or with a feeder and a quality koi food will keep them healthy and growing. A healthy fish continues to grow all its life.

I am often asked about whether fish grow to the size of their surroundings. This is partially true as there is scientific proof that the buildup of certain metabolites (wastes in the water and lesser water quality) will retard growth rates. In contrary, I have seen a ten-gallon aquarium grow 10 pounds of carp. They looked like they could barely move. This was possible because the aquarium received a constant flow of fresh water exchange.

Maintain your pond with the correct filtration and the correct food and your fish will flourish. As they grow and become beloved pets, you can think about increasing your pond size to hold even more fish. The average pond owner increases the size of their ponds 4 times throughout their hobby.

Here are the typical growth rates most pond owners should expect.

Butterfly Koi Fish

Butterfly Koi Fish

  • The first year the fish should grow to 8 inches
  • By the second year, the fish should grow to 12-14 inches
  • By the third year, the fish should grow to 16-22 inches
  • By the fourth year, the fish should grow to 24-28 inches
  • In the later years, growth of 1-3 inches can be obtained

The largest koi I have personally seen have hovered around the 40 inch mark. They are usually of a variety such as a chagoi, or some single color metallic varieties.

Koi – They truly are living jewels. I work in an industry that brings my customers and myself a lot of joy.

This is a guest post by:
Joe Pawlak
Blackwater Creek Koi Farms Inc

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{ 2 comments… read them below or add one }

Giovanni Carlo October 6, 2015 at 10:01 am

They grow fast in the mudpond. based in experience I place koi fry in about 1/4 inch in the mud pond and i about one month its sizes are 3 to 4 inches already.

Tim February 21, 2017 at 8:02 pm

I purchased a house 7 months ago that came with a pond. The water was pretty dank – I couldn’t even see the bottom. After treating it with a small pump/filter and barley flakes I noticed that there were fish in it. Continuing to filter the water I can now see the bottom of the pond (10’x8’x36″) and see that there are 24 fish. I have always wanted a koi pond (one reason I bought the house), but I am unsure how to care for it. I am certain I will need a better pump than I got ($50 on Amazon), and I hear I need to feed the fish, other than that I am stumped. Can you recommend a pump/filter and food? I don’t even know if the fish are koi. Largest is 3-4″, most are 1-1.5″. Does type of fish matter for food purchased?

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