Do Koi Fish Hibernate? All You Should Know About Koi Fish Hibernation

Koi fish are well-known for being gorgeous ornamental fish. Besides, they are also famous for their special hibernation.

Do these aquatic creatures hibernate in cold months? Although these carps don’t literally hibernate, they enter a period called torpor, in which they are almost immobile to conserve energy.

If you are curious about Koi fish hibernation, it’s time to dive into this article to get an in-depth explanation. Let’s get started!

Do Koi Fish Hibernate?

As shared earlier, Koi fish don’t really experience actual hibernation like other hibernating animals like bears, bats, or squirrels. They go into a “torpor” state.

What is the “torpor” mode? It’s merely a metaphor for describing hibernating for a brief period in freezing ponds.

What is the primary purpose of this state? When they enter this short-term hibernation mode, they can conserve their energy during the cold months to utilize that energy for other energy-intensive activities.

You may assume that the cold temperature will benefit this fish species, but this is not always the case.

Although Koi belong to the cold-water carp family, they aren’t tropical fish. Thus, prolonged cold and gloomy periods are still detrimental to their health.

For instance, the cold temperature in wintertime may harm the immune system of these carps or cause it even wholly to shut down.

Moreover, it’s worth noting that these fish may find it hard to awaken from their “torpor” state. They need time to slowly wake up from hibernation rather than awakening suddenly.

If you want to know how Koi awaken from their semi-hibernation, you can watch this video:

If you’re planning to keep this fish type, it’s a good idea to learn about their dormancy period so you can help them get through this cold period.

Koi fish in torpor mode

Torpor mode of Koi fish

What Happens When Koi Fish Hibernate?

Although Koi fish go into “torpor” hibernation, they don’t just sleep. When they hibernate, what happens? Below are some changes during their dormancy:


Since food is usually scarce during cold months, the metabolism of Koi carps slows considerably to conserve energy.

You shouldn’t feed them if the water temperature dips below 52 degrees Fahrenheit. They refuse to take in food if you keep feeding them since they are about to enter a dormancy state.

Besides, hibernate koi fish attempt to avoid moving about as much as possible to conserve energy. They will move around occasionally, but not with the dorsal fins.

Their movements are sufficient to keep their joints from freezing while they strive to stay motionless at the water’s bottom.

koi fish in dark pond

They slow their metabolism.

Immune System

The immune system of these aquatic creatures also starts to slow down like their metabolism during the wintertime, which is the most severe hazard to these carps, especially sick fish.

When the cold season ends, parasites and germs making your carps sick grow active before the immune system goes back to regular operation.

It makes them more susceptible to illness after the wintertime ends. Keep a lookout for these carps when spring arrives!


Even while sitting at the pond’s bottom, this species will find a way to keep upright. Tucking the dorsal fins underneath their body keeps them in this posture.

Remember that these dorsal fins are responsible for up-and-down or side-to-side movements. As a result, tucking these fins means that the carps remain upright and practically motionless.

That means they can still float in the water bottom and travel from one location to the next without utilizing the dorsal fins.

slow moving koi fish

They move slowly


Most people think that the bottom of the pond has a colder temperature than other layers of water. However, the truth is the opposite.

The water in this area will be warmer during winter and cooler during summer. That’s why hibernation koi fish are usually at the bottom of the water.

During the hibernation period, these carps tend to form a line in the even space and same direction.

This action aims to attempt to occupy space where the water is warmer rather than sharing body heat since this species belongs to cold-blooded carp.

Their behavior is mainly affected by the temperature. These carps may also gently circle the pond if the temperature in the pond is around 45 – 55 degrees Fahrenheit.

They may also sunbathe themselves when the temperatures are favorable, particularly if the water has yet to freeze.

They will remain motionless if the temperature falls under 45 degrees Fahrenheit. During this time, you shouldn’t feed them.

However, they still try to get essential nutrition by scouring the pond’s sides or bottom for some nutritious algae. This way, they can receive the necessary calories and conserve energy.

Bodily Function

As you can see, Koi fish slows down everything during wintertime to conserve energy. Thus, no bodily function is exceptional.

They slow their respiration to save energy and compensate for the lack of oxygen owing to icy cover. The digestion of these aquatic creatures is also slow.

The frigid temperatures cause the blood of these carps to flow slowly throughout their body. It is among the main factors driving them to go into hibernation.

So, these fishes change to adapt to harsh winter conditions. Although they fall into the “torpor” mode, you still need to care for them.

If the water temperature drops under 30 degrees Fahrenheit, they might still freeze to death.

How to care for your hibernating Koi fish? You can apply some tips below:

  • Check the temperature of the water in the pond constantly.
  • Reduce feeding them.
  • Clean their ponds.
  • Transfer them to another indoor pond with warmer water.

two koi fish swimming slowly

The bodily function happens slowly


Koi are hardy fish and can tolerate a wide range of temperatures, but they cannot survive in freezing water.

If the temperature of their pond drops below freezing, the koi will go into a state of dormancy. Their metabolism will slow down and they will become sluggish.

In some cases, koi have been known to survive for several months in an icy pond. However, once the ice begins to thaw, the koi will quickly revive and resume their normal activities.

Water temperatures below 50 degrees Fahrenheit can be fatal for koi fish. As a result, it’s important to take steps to keep your koi pond warm during the winter months.

One way to do this is to use a pond heater. Pond heaters are designed to maintain a consistent water temperature, and they can be an invaluable tool for warming your koi pond.

Another way to keep your koi pond warm is to place it in a sun-lit location. If possible, try to position your pond so that it receives direct sunlight for at least part of the day. The sun’s rays will help to heat the water, making it more comfortable for your koi fish.

Finally, make sure to insulate your pond with a pond cover or tarp. This will help to reduce heat loss and protect your koi from the elements. By taking these simple steps, you can help ensure that your koi stay healthy and happy all winter long.

What month do you start feeding koi fish?

Spring is the time of year when koi fish wake from their winter dormancy and begin to actively feed again. As the water temperature starts to rise, koi will become more active and begin to search for food.

For this reason, it is important to start feeding koi fish in the springtime so that they can get the nutrients they need to grow and thrive.

While koi can be fed throughout the year, it is best to limit their food intake in the winter months when they are less active.

Wrapping Up

After reading this article, have you deeply understood the Koi fish hibernation?

The dormancy time of these carps is not exactly the same as that of other animals. Instead, they experience “torpor” mode or a brief hibernation period.

When a dormant state happens, this species will slow down everything to conserve energy, including its metabolism, immune system, other behaviors, and bodily function.

Hopefully, this article will be helpful for you. Thanks for taking the time to follow this post!