Do Koi Fish Hibernate in the Winter?

Do koi fish hibernate in the winter? Due to the fact that koi fish require as close to a natural environment as possible, we know that indoor and outdoor koi fish ponds are ideal. But what happens if you have outdoor koi fish when winter rolls around? After all, won’t your pond freeze when temperatures drop? If so, won’t your koi fish freeze too?


These are all critical questions that any new koi owner will have during their first year with their koi fish. Put simply, yes, koi fish do hibernate during the winter. That being said, this long winter sleep isn’t quite the same as it is for other hibernating animals. Unlike bears, for example, that stock up on food and sleep for the entirety of the winter season, the way koi fish hibernate is a bit different.


Today, Koi Fish USA will be answering all of your questions revolving around whether or not koi fish hibernate in the winter. We’ll discuss what happens when koi fish hibernate, and we’ll talk about ways you can continue to care for your koi fish while they hibernate. With this guide, you’ll be better prepared to care for your koi fish appropriately once winter is here. There is no better time to prepare!

Do Koi Fish Hibernate?

As discussed, koi fish do hibernate in the winter months. But rather than stocking up on food in preparation for winter and sleeping, koi fish remain at the bottom of their pond, floating upright, and both their heart and metabolism slow down as they enter hibernation mode. Rather than sleeping, you might think of koi fish hibernation as a state of rest. While in this state, koi fish conserve their energy. As a koi fish owner, it’s important that you know that while your koi fish are in this hibernation state, they can’t be “snapped out of it.” Rather, they will ease themselves out of it at a slow pace once the months become warmer.


With all of this being said, it’s critical that you know that while this is a natural way of life for koi fish, hibernation can still prove unhealthy for them during these extended periods of cold and dark. In fact, their immune system can be damaged and, in severe cases, even shut down entirely. For this reason, it is valuable to have all of the necessary knowledge so that you can plan your outdoor koi pond’s winter properly. When you are aware of all of the ways to best support your koi fish during hibernation, you can greatly reduce the chances of bad consequences.

What You Should Know About Koi Fish Hibernation

Now that you know that koi fish hibernate during the winter, you may be wondering what the process looks like and what you need to know. Here are some of the most important things to keep in mind when your koi fish go into hibernation.

1. Hibernation Behavior

Due to the fact that koi fish are coldwater fish, many people assume that they thrive in cold environments. This isn’t necessarily true. In fact, one of the most common hibernation behaviors you’re likely to notice in your koi fish is that they’ll remain at the bottom of your pond. Koi fish elect to remain at the bottom of the pond during winter months because the bottom of the pond is warmer. The opposite is also true. Koi fish tend to stay closer to the surface of the water during warmer months because the bottom of the pond is cooler.


Another interesting behavior you will notice in your koi fish during hibernation is that they all space out evenly and face the same direction. Koi fish tend to assume this formation because they’re trying to take up more space where the water is warmer.


In terms of koi fish activity during hibernation, this is largely based on the temperature of the water. When the water temperature is below 45 degrees Fahrenheit, koi fish tend to remain still. During this time, it is recommended to avoid feeding. But don’t worry- your koi fish aren’t starving. During this time period, koi fish will often scrape the sides of the pond to eat algae, which is nutritious.

2. Position

In terms of their position in the pond, koi fish will sit upright during hibernation. They maintain this position at the bottom of the pond by tucking their pectoral fins underneath their bodies. When these fins are tucked away, it ensures that the koi fish remains upright and almost entirely still.

3. Immune System

Because koi fish have to conserve their energy during hibernation, their immune system is also known to slow down significantly. Unfortunately, this is the biggest threat to koi fish during hibernation in terms of their health. You should always be careful to look for the most common signs of illness in koi fish to be sure you are doing all that you can to prevent sickness when their immune system is slowed down.

4. Hibernation Metabolism

Finally, you will notice changes in your koi fish’s metabolism once hibernation sets in. In the wild, koi fish will purposely slow down their metabolic process due to the fact that it is hard to find food in the winter. The same process applies when they are bred in captivity, even with an endless supply of food provided, and this is one of the reasons you should be careful to limit feeding once your pond’s temperature drops to 51 degrees or lower.


If you happen to try to feed your koi fish during this time, you’re likely to notice that they refuse to eat due to going into hibernation mode. They will slow their metabolism and cease to move as much. Although they will move from time to time, they’ll stop using their pectoral fins as often. They will only move as much as is needed to prevent their joints from freezing while they remain at the bottom of the pond.

How to Care For Your Koi Fish During Hibernation

So what should you do to ensure your koi fish are properly cared for during hibernation? Keep the following things in mind to provide the best possible environment for your koi fish during hibernation.

1. Be Sure to Move Your Koi Fish If Needed

If you live in a place where the winter season is particularly severe in terms of temperature, it is likely that your pond will freeze completely. In this case, you should definitely move your koi fish indoors, either into an indoor pond or into individual tanks. This way, they won’t have to be exposed to harsh cold temperatures. Once moving your koi fish indoors, you can simply simulate the temperature in their tanks in order to trigger hibernation mode. This is the ideal situation for keeping your koi fish happy and healthy.

2. Continue Keeping Your Pond Clean

During the winter months, you should make sure that your pond is free of bacteria and parasites. In order to do this, treat your water for at least two weeks before your koi fish go into hibernation. In doing so, you will limit the amount of waste produced which can prompt bacteria to latch on to your koi fish once they come out of hibernation.

3. Reduce Feeding Appropriately

Finally, reduce feeding appropriately during winter. If the temperature in your pond is 55 degrees or above, you can feed your koi fish as you usually would. Otherwise, you should stop feeding your koi fish even before the temperature drops to 45 degrees. The longer you feed your koi fish once temperatures reach this level, the more they will eat and the more difficulty they will experience slowing down their metabolism during hibernation.

The #1 Online Koi Fish Seller: Koi Fish USA

Now that you know all about koi fish hibernation, you can take the necessary steps to ensure the winter goes smoothly and that your koi fish remain happy and healthy. In the meantime, are you looking for an online koi fish supplier that you can depend on to meet and exceed your expectations? Look no further than Koi Fish USA!


With over 25 years of combined experience in the online koi and goldfish industry, we are the experts you can rely on. We have a passion for providing the safest, most high-quality koi fish on the market, all at a price to suit your budget. So check out our selection of butterfly koi, standard koi, and goldfish today! Stay tuned to our blog for more tips on all things koi fish ownership.