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How Fast Do Koi Grow in a Pond?

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Understanding the growth rate of your koi fish is extremely important!

Whether you breed koi fish, enter your fish into competitions, or simply want to make sure you don't have overcrowding issues in the future, knowing how fast koi grow and how big they get should not be overlooked.

So, let's take a closer look at how fast koi grow, the variables that affect koi growth rate, and learn how you can make them grow faster.

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How Fast Do Koi Fish Grow?

Koi fish grow at a variable rate. The average koi will increase its length by about 8 inches (20 centimeters) or so in the first year, reaching roughly 15" (38 centimeters) by the end of year two, then reach its full adult size of 24+ inches (up to 36 inches for some jumbo koi carp) by the time it reaches 3 to 4 years old. Your koi may continue to grow slightly over the next several years, but the bulk of their growth happens in the first 3 to 4 years.

Koi Growth Chart

Koi growth chart

You can use this knowledge to get an idea of how old your fish are. For example, a 5-inch koi will be roughly 6 months old.

Of course, this growth can vary dramatically depending on the type of koi you have and the variables we'll discuss below.

Age

The age of your koi will have an impact on how fast they grow. You'll notice in the chart above, your koi will grow rapidly in the first 3 to 4 years of its life. That growth will slowly taper off in the following years.

Water Temperature

The temperature of your pond water will also affect the speed at which your koi fish grow.

If you live in a region with colder temperatures and want your koi to grow faster, invest in a pond heater. In warmer waters, their metabolism is increased resulting in more activity and appetite which will promote growth. If the water is too warm, however, it can cause stress and stunt the growth of your fish!

On the flip side, when the water is colder your fish enter a state of torpor to conserve energy. This may result in reduced appetite and growth. Raising the temperature of your pond water with a pond heater will help your fish actively grow during these colder months.

According to at least one study, the ideal temperature for maximum koi growth is between 75 - 80 degrees F (24 - 27 C).

Water Quality

The pond water that koi live in should be consistently monitored for pH, KH, salinity, and dissolved oxygen content to keep their living space healthy.

Koi are more likely to become stressed or ill if any of these factors are not within a healthy range. This stress can result in harmful hormone fluctuations as well as decreased growth rate, appetite loss, weakened immune system, among other things.

Be sure to test your water regularly with a pond water test kit to ensure a healthy environment for your fish.

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Nutrition

While you technically don't have to feed koi fish in a pond (in the right environment), feeding your koi high-quality food will help promote faster growth.

Poor nutrition can cause stunted growth, illness, and even death for your koi fish. What you feed them is extremely important so do your due diligence when selecting a product to feed your fish.

We highly recommend Kaytee Koi's Choice Premium Fish Food as it contains all the essential nutrients and proteins required for optimal growth, color, and longevity.

Kaytee Koi's Choice Premium Fish Food

Kaytee Koi's Choice Premium Fish Food

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Pond Size

While pond size won't affect how big your koi will get (contrary to popular belief), it can affect how fast your koi grow.

This all comes back to stress on your fish. A koi pond that is overcrowded or not large enough to support your fish may cause them stress, which we've learned can cause harmful hormone fluctuations as well as decreased growth rate, appetite loss, etc.

You'll hear different recommendations for how many koi you should have in a pond to avoid overcrowding, but the general rule of 1 adult female koi per 1,000 gallons (3,785 liters) of pond water or 1 adult male koi per 500 gallons (1,893 liters) will maximize their growth potential. You can certainly get away with 1 koi per 250 gallons (946 liters) of pond water, but for them to grow faster we recommend more water volume per fish.

And remember, your fish will grow, so estimate enough room for adult koi, not the size they are when you buy them.

Genetics

Genetics plays a huge role in how fast, and more so, how big your koi will get. In even the best pond environment optimized for koi growth, your koi won't be able to outgrow its genetic potential.

How Can I Make My Koi Grow Faster?

The first three years of a koi’s life are where you'll have the greatest potential for growth. So, try to maximize their growth during this time with these 2 simple tips to achieve the best results.

Optimize Their Environment

Providing the optimal environment for your koi will help them grow faster and live longer. You can do this by:

  • Regulating water temperature: As mentioned before, the temperature of water affects digestion, metabolism, appetite, and other things. Keep the water between 75-80 degrees F for best growth potential. You can monitor the temperature of the water with a pond thermometer.
  • Maximizing pond water quality: A koi pond should have a pH between 7.5 and 8, dissolved oxygen levels of at least 7 ppm (parts per million), and as little ammonia, nitrates, and/or nitrites as possible. Regularly test your pond water with a pond water test kit to ensure all of the parameters are within range.
  • Not overstocking your pond: If you want to grow your koi the fastest, stick to the general rule of thumb: 1 female for every 1000 gallons (3785 liters) or one male per 500 gallons (1,893 liters).

Feed Them Quality Food on a Schedule

Along with optimizing your koi's environment, you can help them grow faster by providing them high-quality nutrition on a set schedule.

  • High-quality nutrition: While koi can survive on insects, plant matter, and other organic matter, high-quality fish food will help your fish grow faster and live longer.  We recommend Kaytee Koi's Choice Premium Fish Food to help your fish grow faster and live longer as it contains all of the essential nutrients they need for optimal growth, color, and longevity!
  • Feeding schedule: Keeping your koi on a set feeding schedule will help you make sure they're getting all the nutrition necessary for optimal growth while also monitoring how much food they eat each day. Check out our guide on how often you should feed koi fish in a pond for more information.
Kaytee Koi's Choice Premium Fish Food

Kaytee Koi's Choice Premium Fish Food

Price:
Buy Now on Chewy
Buy Now on Amazon

Clicking this link to make a purchase may earn us a commission at no additional cost to you.

How Big Do Koi Get?

Koi fish on average can grow up to 2 - 3 feet long and weigh around 35 pounds. Some big koi varieties, like the Chagoi Koi, can grow up to 4 feet long!

How Long Do Koi Fish Live?

Most koi fish will live for roughly 20 - 30 years in the right environment. Incredibly, the longest recorded koi fish lived to be 226-years old!

Of course, there are many factors that will affect their longevity. Check out our guide titled How Long Do Koi Live in a Pond to learn more about their lifespan, tips to improve their longevity, and more!