Can Koi Fish Survive Winter in Outdoor Pond? {Things You Need To Do}

Are you keeping your koi fish in an outdoor pond?

Is winter coming and are you thinking can koi fish survive winter in outdoor pond?

Is there anything special you need to do?  Find out below

Can Koi Fish Survive Winter in Outdoor Pond?

Yes, Koi fish are hardy fish and can withstand a wide range of conditions. Koi fish can survive in temperatures as low as 5 degrees Celsius, which means they can survive in outdoor ponds even during winter. They can even survive lower temperatures as long as the water does not freeze solid.

How Cold Can Koi Survive?

Koi are cold-water fish that can thrive in a wide range of water conditions. They can thrive in water as cold as 0 degrees Celsius without encountering a problem. The only time water can become too cold for a koi fish is when the water freezes solid.

This phenomenon occurs due to the kind of metabolism koi fish possess. Koi fish regulate their body metabolism to suit the temperature of their environment.

They do this so that as the temperature of the environment reduces, their activities also decrease.

At 50 degrees Fahrenheit, koi fish experience reduced activity. They do not swim much and also will not eat much of what you give to them. You have to feed them only two to three times a day.

The type of food you feed them at this point also matters. You have to feed them fatty and vitamin-rich foods.

These foods will help them store fats for days of hibernation, so your fish will have enough nutrients to carry on during a hard time.

When the temperature gets to 40 degrees Fahrenheit, your koi fish will hibernate and experience no activity.

They will not swim, neither will they feed on whatever you give them. You have to stop feeding them at this point so you won’t contaminate the water.

No matter how cold the water temperature is, your koi fish will be alive, but only in a hibernated state. It will stay alive as long as it can unless the water freezes. Once the water freezes, your koi fish will die.

You have to make sure the water does not freeze up while your fish is hibernating. Ensure you provide what your koi fish needs.

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How Do Koi Fish Survive Winter?

Koi fish survive the winter by entering a semi-dormant state. It may be confused with hibernation but it’s a close similarity to what is known as torpor.

The entire metabolism of these koi fish slows down and the state that you may see them in is somewhere in between hibernating and half asleep.

This occurs when the temperature drops below 50 degrees Fahrenheit. Koi fish are not eating during this time.

Underneath 40 degrees Fahrenheit, it is much more obvious to witness this torpor state.  This is how koi fish survive the winter without needing to eat any food.

How To Keep Koi Fish Alive in Winter?

There are actions you need to take regarding your koi pond during winter. You need to take these steps to keep your koi fish alive during winter. Here are what you should do to your pond during winter;

  • Deepen the pond: The first thing you should do to your pond is to deepen it. You have to increase the depth of your pond. During winter, the top of the pond starts freezing before it gets to the bottom.

Increasing the depth of the pond will ensure that the water in the pond does not completely freeze up. You have to increase the depth of your koi fish pond to ensure its safety during winter.

  • Use pond de-icer: You also need to make use of pond de-icers for your koi fish pond during winter. The de-icer is a floating device that disrupts the formation of ice at the surface of the water. It will also prevent the formation of ice in the water.
  • Set up pond heater: You have to set up a pond heater for your koi fish pond. The pond heater will help keep the water heated, preventing it from freezing. You have to be careful while regulating the temperature of the heater to prevent causing too much heat.
  • Use water devices: Using water devices like a filter, air pump, fountain, etc., will help prevent ice formation. These devices will cause water movement, and water movements will reduce ice formation in the water.

These water devices keep your pond suitable and comfortable for your koi fish. You need to add these devices and take certain steps to provide a suitable habitat for your koi fish.

Can Koi Fish Freeze and Come Back to Life?

Koi fish can withstand a lot of adverse conditions that include low temperature. They can withstand temperatures as low as 40 degrees Fahrenheit but will not come back to life after freezing. Once koi fish get frozen, they become dead, and they can’t come back to life.

Koi fish do not get frozen; they only hibernate. When they hibernate, they may appear dead, but they are very much alive. They only reduce their activities and body metabolism, causing them to survive through the winter period.

During winter, you have to ensure the water does not freeze up and a sufficient amount of oxygen. If oxygen gets exhausted in the pond, the koi fish will die. You have to ensure there is enough oxygen for your koi fish.

When the pond becomes frozen, there will be a limited amount of oxygen in the pond. The ice on the pond’s surface will prevent the interaction of the pond water and the atmosphere. It will reduce the amount of oxygen that gets into the pond, causing your fish to suffocate.

You need to make sure your fish pond does not get frozen for the safety and wellbeing of your koi fish.

How Do I Keep My Koi Pond from Freezing in the Winter?

To keep your koi pond from freezing, you need to consider some factors and take the above actions. You need to increase the depth of your pond to prevent complete ice formation. You can also make use of floating deicers to disrupt the formation of ice at the surface of the pond.

You can also make use of aquarium devices like air pumps, filters, heater, etc. These devices will also help prevent the formation of ice in the pond.


Koi fish can survive winter in an outdoor pond if you take necessary actions. You have to prepare your pond to make it suitable for your koi fish. Providing the right conditions will help your koi fish survive during the winter.

John Brandon

John has kept fish all his life (since he was about 5). He started with keeping guppies and fell in love with fish keeping almost straight away. That was 40 odd years ago. These days John still keeps fish and currently has two large tanks where he keeps many different types of fish such as Angelfish, Neon Tetras, Goldfish, Guppies and many more.

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