Do Koi Fish Hibernate? All Facts You Must Know

Do Koi Fish Hibernate? All Facts You Must Know

Koi fish are always a beautiful addition to your pond. They are generally peaceful toward other fish species, come in a wide range of vivid colors and patterns, and can be lively, engaging neighbors in the water. Do koi fish hibernate in winter?

Koi fish do not really hibernate but during the winter, koi fish go into torpor, a semi-dormant state. In cold weather, feeding fish is not necessary or advisable. Aeration is essential for ensuring that your fish survive till spring. With the right care, most pond fish like koi can endure a brutal winter.

Torpor is a condition very similar to hibernation. It leads to a motionless state to conserve energy and reduce the organism’s need for food, but it is not technically hibernation. Most koi fish go into torpor for a period of three to four months. Some fish are known to go into torpor or hibernate for a much longer time than others.

You might be asking what is hibernation. Hibernation is the conservation of energy to endure bad weather or a shortage of food. It entails physiological adjustments such as a lowering of body temperature and a slowing of metabolism.

In this article, I will explain hibernation and what you should expect for your Koi fish in the winter season.

How to know when koi fish are going to hibernate?

There are a few notable things to know when koi fish are going into hibernation (torpor). Your Koi fish become less active and sluggish in cooler water. As their metabolism slows, their appetite decreases, and they eventually stop eating. You may also see your Koi fish begin to change colors as they get ready for hibernation.

When the water in your pond reaches about 50 degrees Fahrenheit, your Koi fish will begin a period of semi-hibernation or torpor. Koi fish are still vulnerable to diseases, so keeping the water quality up during this period is crucial.

What changes should you expect when koi fish goes into hibernation?

You can check their status from their position. They can “sit” on the pond’s floor and remain standing. One way they stay in this posture is by tucking their pectoral fins under their bodies.

Pectoral appendages are responsible for lateral and vertical motion.

Therefore, your koi fish will stay vertical and practically “still” during hibernation.  We call them “still” because they can stay afloat without using their pectoral fins and travel very slowly from one place to another.

How does a koi fish’s body respond to winter and hibernation?

Bodily process

Everything in a koi fish’s body slows down during winter. They slow their breathing to preserve energy and compensate for the reduced oxygen levels caused by the ice. One of the reasons koi fish go into a hibernation-like state in cold weather is that their blood moves more slowly through their bodies. Even their digestion slows down, which is to be anticipated, given how little they eat in the winter.

Immune system during the winter season

Your koi fish are most at risk from the weakened immune system they experience during the winter. The parasites and bacteria that can make your koi ill become active once winter is over, long before the fish’s immune system is ready to fight them off. Due to this, they are particularly susceptible to illness once winter has ended. Although koi are relatively safe during the winter because their immune system slows down, this can be risky once the weather changes. So, you should be on the lookout once spring arrives.

Wintertime koi metabolism

To conserve energy during the winter when food is scarce, the metabolism of a koi fish slows significantly. Because of this, you shouldn’t bother feeding your koi when the water in the pond is below 52 degrees Fahrenheit, and even if you do, they probably won’t consume much. To conserve even more energy, koi fish move very slowly during their semi-dormant state. They’ll remain near the water’s edge, moving just enough to keep their joints from freezing.

Is it okay to feed koi fish while they are hibernating?

Koi fish can make it through the winter without eating because they enter a sort of dormancy. Because their metabolism has slowed and they have lost their hunger, they do not require feeding now.

But because Koi fish are still susceptible to diseases, the water quality must be maintained throughout the event.

Do koi fish require special care during the winter?

If you reside in a region that experiences severe winters and you are confident that your pond will completely freeze over, you may want to consider relocating your koi fish indoors.

In this manner, they can avoid the discomfort of the water’s extreme cold.

You need only artificially lower the tank’s temperature to let them hibernate. This is the best scenario if you want your koi fish to stay healthy and be readily observable.

When do koi fish typically get out of hibernation?

When the water temperature rises and stabilizes, koi fish emerge from their winter dormancy. The late spring and early summer months are peak times for this.

Indicators of your Koi fish emerging from hibernation include increased activity and a renewed interest in finding food.

However, you shouldn’t give food to them right away because they might be unable to digest it. You can begin feeding them after a few days.

You will start to see them more frequently as the water warms up. The colors will also be more intense.


Koi fish don’t hibernate, but when the water temperature drops below a certain point, they enter a torpid state that’s comparable to hibernation. They cease eating and tread water at the pond’s bottom to keep from freezing solid. You shouldn’t worry too much if you come across a frozen pond because they will emerge from this condition once the water warms up.

You should stop feeding the fish when you see them slow down and stop moving around, and you should also consider adding a thawing device, which can be as simple as a football that bobs around and stops a portion of the surface from freezing over. This allows stale air to leave the water and allows for the entry of new air.

Here is another related article you might want to read next: Can Koi Fish Live With Goldfish? Top Facts To Know