5 Reasons Your Koi Fish Aren’t Growing

As a koi owner, you likely expect your koi fish to grow to their maximum size. One characteristic that makes koi fish such recognizable fish is their large size. With fully grown koi fish reaching up to 24" or more, koi are sizeable fish that demand attention.

 Unfortunately, some koi fish owners may find the growth of their koi stunted. While this is worrisome, it is essential to remember that there is an identifiable cause. A variety of factors impact fish development. By knowing each of these factors, you can work proactively to create the best conditions to support the growth of your koi.

 Today, Koi Fish USA will be describing 5 of the most common reasons your koi fish aren't growing. We will explain the reasons for stunted koi fish growth, and we'll also include some helpful tips as to what you can do to rectify the problem. Let's get started!

How Long Do Koi Fish Take to Grow?

Before we discuss some of the most common reasons for stunted koi fish growth, you must have an understanding of how long koi fish take to grow. In most cases, when properly cared for and housed in the right conditions, koi fish can be expected to grow nearly up to an inch per month. Most koi fish reach their full adult length by age 3, reaching 20 inches or more. However, the exact adult length of your koi fish will depend on the species.

Why Aren't My Koi Fish Growing?

1. Water Temperature Impacting Growth

One of the likeliest reasons that your koi fish aren't growing has to do with the water temperature in your pond. Because koi fish cannot control their own body temperature, they heavily rely on the pond's water temperature to regulate their metabolism. Warmer water facilitates faster koi fish growth as it naturally increases appetite. That being said, when the water is too warm, it can actually stunt growth because of the stress it puts on your koi fish. As you can see, there is a fine line between proper water temperature and harmful water temperature when it comes to a koi fish pond. 

We highly recommend keeping your pond's water temperature between 65 and 75 degrees Fahrenheit to support a healthy growth rate. If you measure the temperature of your pond and find that it is too warm, you should consider adding shade. It is also important to note that if you want your koi fish to continue growing during the winter months, it's best to bring them inside to keep them at a more comfortable temperature.

2. Poor Water Quality

Here at Koi Fish USA, we have emphasized the importance of good water quality in koi fish ponds time and time again. When it comes to koi fish growth, the right water quality is once again vital. When a koi fish pond isn't clean, it causes tremendous stress on your koi fish, and this can cause them to stop growing. While stress contributes to a variety of common koi fish diseases, it can also stunt growth. It's also crucial to remember that just because your koi fish pond looks clean, this doesn't necessarily mean that the water quality is good.

The best way to ensure that your pond's water quality is good involves testing it regularly. We also highly recommend performing regular water changes and working proactively to keep waste and other debris out of the water. To learn more about keeping your pond's water quality where it should be, check out our article "Definitive Guide to Koi Fish Pond Maintenance."

3. The Size of Your Koi Fish Pond

Another reason that your koi fish aren't growing might have to do with the size of your pond. While many koi fish owners believe that the size of a koi fish pond doesn't necessarily matter as long as overcrowding is avoided, this isn't the case. A pond with limited space significantly reduces your koi fish's ability to get adequate exercise, a fundamental part of growth. Additionally, too small of a pond can cause your koi fish stress, and, as discussed, stress is a huge factor contributing to stunted koi growth.

As a general rule, the more space you provide your koi fish with, the happier and healthier they will be. Your koi fish pond must be the proper length, width, and depth to support koi fish growth. It's also important to know that deeper ponds typically improve water quality. To learn more about building a perfectly sized koi fish pond, check out our article "How to Build a Koi Fish Pond Step-By-Step."

4. Pond Overcrowding

Like any other animal, koi fish need adequate room to grow, and an overcrowded pond can play a huge role in disrupting koi fish growth. When a koi fish pond becomes overcrowded, you'll quickly find your koi fish competing for food, resulting in high levels of stress and hostile koi behavior. Additionally, a crowded koi fish pond also means more waste- a huge contributor to poor water quality.

So how much space do your koi fish need to grow properly? As a guideline, we recommend that your pond hold 1,000 gallons of water at minimum. Your pond should also have 10 square feet of surface area per koi fish and 10 gallons of water per inch of koi. If you have found that your koi fish pond has become overcrowded, we highly recommend doing the work to expand your pond. When given the proper amount of room to thrive, your koi fish will grow at a healthy rate.

5. Poor Koi Fish Diet

Finally, it's a good idea to consider the diet of your koi fish if you've noticed that they aren't growing properly. One of the biggest mistakes that we see koi fish owners make regarding diet involves the use of low-quality koi fish food that is high in fats and carbohydrates. These types of foods are difficult for koi fish to digest properly. Not only will improper nutrition stunt koi fish growth, but it is also known to cause high stress levels and even illness.

If you want to keep your koi fish healthy and support growth, feeding them the correct type of food is essential. Regularly provide them with high-quality food explicitly made for koi fish. There are even some koi fish food brands formulated to boost growth. When your koi fish are adequately fed, their metabolism works like a well-oiled machine. They'll have the best chance of reaching a considerable size.

Set Your Pond Up For Success With Koi Fish USA!

Now that you know five of the most common reasons your koi fish aren't growing, you have all of the information you need to offer the best conditions for growth. Often, doing your research and gathering all of the facts is vital to the health and happiness of your koi. The same rule applies when choosing where to purchase koi fish for your pond. Luckily, you've found the best of the best here at Koi Fish USA!

At Koi Fish USA, we are proud to be the most trusted online koi fish seller. We offer a variety of stunning butterfly koi, standard koi, and goldfish. No matter what variety you're looking for, we likely have exactly what you need in stock! Our customers also love that we offer a 14-day guarantee on every fish we sell because we are confident in the quality of our selection.

As always, stay tuned to our blog for regular informative content on all things koi fish, goldfish, and pond maintenance. If you have any questions or concerns, feel free to contact us so that we can assist you.