An Ultimate Guide To Koi Fish Growth Rate – Koi Carp Size And How Fast Do Koi Grow

If you consider buying some beautiful and healthy koi fish, you must wonder how big they can get so that you can choose the right pond.

When mature, this carp can reach a length of 36 inches. Their monthly growth rate can be 0.8 inches. However, this rate varies from species to species.

We’ll go through the koi fish growth rate and other important details like factors that can influence your fish’s development. Let’s read on to discover!

Koi Fish Growth Rate

For the first six months of this carp’s life, it grows at a rate of 0.2 inches each day, or around 0.8 inches every month.

Your carp should be roughly 9.2 inches long and weigh around 8 ounces at the age of one.

There are various elements to consider while determining the size of the fish. They include:

Genetics of Koi

The genetics of the fish play a significant role in identifying its size. If a koi don’t have the required specific traits, it won’t grow into a huge specimen, no matter how great the pond conditions are.

Koi’s Pond Water

Warmer water promotes a faster metabolism. The two factors work together to provide higher growth rates.

If you live in a region where your pond freezes in the winter, the super cold time will reduce your fish’s development.

Koi’s Diet

If your koi aren’t getting enough food or the correct kind of nutrition, their growth rate will suffer.

The fish will thrive on the right diet, which has the right balance of carbohydrates, proteins, and lipids.

two adult koi fish

Genetics, water, and diet are important to these carps

Koi Fish Growth Chart

Because this chart works on the typical koi’s development rate, not all of them will be the exact size.

The chart below is merely to give you an idea of what to expect when the koi grow bigger.

Age Expected size (inch)
1 month 1.1
3 months 3.6
6 months 5.1
1 year 9.1
1.5 year 12.6
2 years 15.6
2.5 years 18
3 years 20
3.5 years 21.6
4 years 23.4
5 years 25.7
6 years 27.3
7 years 28.5

How Fast Can Baby Koi Fish Grow?

What type of koi you raise will determine the color and size of each baby carp. As the koi matures, you can expect it to go through the following stages.

Week 1 to 6

A baby koi can grow about 0.03 inches every day until it reaches the sixth month. So, it will be about 0.20 inches long by week 1 and 1.2 inches long by week 6.

The young koi may be brown at this stage, or it may be the red or orange we see in adults. However, the colors will not be as brilliant as they can be when the koi grow up.

Month 2 to 6

Your koi will be around 1.6 inches long by two months, and by six months, it might be up to 5.1 inches long.

At this point, the koi’s color should be changing. You may notice that it becomes more vibrant and deeper.

Month 7 to 11

When the koi reaches the age of six months, its development rate slows to 0.2 inches per day until its second year.

Your koi will be around 5.8 inches long by the seventh month, and it will keep growing at a steady rate.

Year one

By this time, your koi can be around 9 inches. Its growth rate is 0.21 inches a day.

Year two

Your koi will be around 15.6 inches in its second year. As it gets older, the daily development rate will slow down.

Year three

Some species have already reached adult size, measuring around 15 to 16 inches, while others may grow 20 inches or even more in the third year of their life.

a big koi fish

The growing process slows down when the fish matures

How To Increase Koi Growth Rates – Help My Koi Grow Faster

The water and diets significantly affect how big your koi can get. Hence, you need to focus on the two factors when raising fish.

Here are some tips to maximize the living conditions of your koi:

Tank size

The rule of thumb is that an adult koi requires at least 250 gallons of water. If you have a female koi that can breed, you need to give it 500 gallons.

However, instead of keeping this species in a tank, raising them in a pond would be perfect. This reservoir must be at least 1,000 gallons in volume and three feet in depth.


The water temperature should be between 60 and 75°F. Although koi can tolerate temperatures both above and below this range, water quality can degrade outside of this preferred temperature.


You should purchase protein-rich pellets that offer adequate minerals and vitamins for your koi.

Besides, regardless of the expiry date on the package, keep the food securely and throw away any leftovers after six months.

koi pond with plants

Try to give your carps the best conditions

How Big Do Koi Fish Get? Common Koi Carp Size

Koi carp size can be between 23 and 36 inches long, with some jumbo species reaching 50 inches.

Indoor carps can also achieve an impressive size if their pond conditions are perfect and the pond is big enough.

Frequently Asked Questions

Can koi grow bigger in a small pond?

Many people believe that koi cannot grow to their full-size potential in a small pond, but this is not necessarily true.

While it is true that koi will grow more slowly in a smaller pond, with proper care they can still reach a respectable size. The key to success is to maintain a proper balance of nutrients and oxygen in the water.

A pond that is too shallow will not have enough oxygen for the fish to grow faster, while a pond that is too deep will make it difficult for the koi to access the food they need.

In addition, regular water changes are essential to keeping the koi healthy and preventing them from becoming stunted. With the right care, it is possible for koi to reach a good size even in a small pond.

Koi are omnivores, and in the wild, they feed on a variety of plant and animal life.

In captivity, they are typically fed a diet of pellets and other commercial foods. This diet is not as varied as their natural diet, but it still provides them with the nutrients they need to thrive.

Because koi fish are able to survive for long periods of time without food, they are often used in research studies on fasting and starvation. For example, a study published in 2016 found that koi fish were able to survive for over six weeks without food by entering a state of suspended animation.

This research could have important implications for humans, as it may one day be possible to enter a similar state during surgery or long-distance space travel.


It’s good that you spend time finding how big your carps will get, as it can help you plan its habitat properly.

Aside from the pond conditions and diets, the species you raise is also a crucial factor in determining the size of your carp.

Hopefully, you will find this article helpful. It would be best to apply the tips we have shared to offer your fish the best conditions.

Thank you for reading!