An Ultimate Guide To Koi Fish Growth Rate – Everything You Need To Know

If you consider buying some beautiful 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:


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.


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.


If your carp 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.

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 carp grows 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

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 carp 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 carp 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 carp grows up.

Month 2 to 6

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

Your carp 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 pet can be around 9 inches. Its growth rate is 0.21 inches a day.

Year two

Your fish 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.

The growing process slows down when the fish matures

How To Increase My Koi Growth Rate?

The water and diets significantly affect how big your carp 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 carps:

Tank size

The rule of thumb is that an adult koi requires at least 250 gallons of water. If you have a female carp 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 carp 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 carps.

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

Try to give your carps the best conditions

How Big Do Koi Fish Get?

Outdoor carps can grow 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.


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!