Summer is over. Fall is here. And winter pond care is quickly on your mind with snow in the forecast.

For our beloved Koi, what should we do?


How to Winterize Pond for Fall and Winter

The following topics are important to know for winter Koi care and will be covered in this article:

  • Water temperature vs. feeding
  • Medicating the pond
  • 4 pond housing options for fall and winter
  • Winter pond prep Q&A


Fall (as well as spring) is a vulnerable time for Koi because water temperatures fluctuate and start dropping.

If we do things wrong, our Koi may not endure the long winter and arrive in the spring unhealthy. So it is vital to prepare for Koi winter survival. Use this article to see our best tips and products for your pond in winter.

We will finish up by also covering some common questions about Koi winter prep in the Q&A section. Ask a question at the end of the article if you want to learn more. We also welcome you to explore more about our Koi for sale online.

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Example of Koi Pond Cover in Winter

There are many options for setting up your pond for the Winter months. We find the design of this pond cover for winter to be especially beautiful and proud to say they are also a Kodama Koi Farm customer. When you want to decide how you will take care of your pond fish in Winter, you will have the following options to consider:

  1. Keep your koi in the pond for Winter
  2. Move koi to a holding tank inside a garage or enclosed space
  3. Build a greenhouse to cover your pond
  4. Cover your pond with solar cover used for pools

The below example is a greenhouse built to cover the entire pond in Winter.

Winter Koi Pond Water Temperature vs. Feeding

Leaf in water

Many times water temperature is overlooked in winter pond management.

It is more important than you think, especially in the spring and fall when water temperatures fluctuate, because Koi are cold-blooded. In other words, they cannot control their body temperatures. Instead their environment does.

When it is hot outside in summer, they become hot. When it is cold in winter, they become cold.

As a result, when water temperature is warm, Koi can eat and digest more. Their immune systems work better. When the water is cold, vice versa.

So as fall approaches and water temperatures start dropping on your pond thermometer, we must watch water temperature closely because their digestion rate changes. We must change the feeding program accordingly. Their immune systems start declining, too.

About 65–68 °F is the turning point.

Schedule for feeding koi based on water temperature

Above is a chart of recommendations by Koi food brand (yellow boxes means it is ok to use).

The most common mistake I see is that owners feed as much as their Koi can eat even in the fall and winter. Owners think they are hungry because they ask for food. They may be eating, but it does not mean they can digest the food properly.

If you keep feeding them when they cannot digest, these Koi will die by or in spring because of poor digestion.

It may look harsh not feeding your Koi for as long as 6 months (depending on where you live), but it is much safer for them. So at optimum water temperature ranges, ensure you feed your Koi as much as possible. That helps your Koi build their bodies’ reserves for winter. In other words, feed as much healthy food as you can (like KKF Wheat Germ All Season) while they can both eat and digest it.

We highly recommend you purchase a pond thermometer so that you are able to better keep track of your temperature.

Koi Pond in Winter & Medication

Medicating the entire pond twice a year, once in spring and once in fall, is also a very important practice.

At lower water temperatures, as I said above, Koi are more vulnerable. So before it turns too cold in the winter, ensure your pond and Koi are parasite-free. These are two of our favorite products for treating your pond for a successful winter.

Buy Koi Prazi for preventing parasitic flukes

Buy Ich-X Water Treatment for treating parasites

At around 50–55° F, treat your pond with Koi Prazi with Ich-X water treatment or a similar product such as Terminate (these are equivalents of Proform-C).

During winter, pathogens will be dormant like Koi; but when spring comes, they will become more active quicker than the Koi will. So it is important that your pond is parasite free when your Koi are waking up in a vulnerable condition.

For the same reason, it may also be a good idea to feed medicated food with antibiotics (see how to make your own) to prevent potential bacteria issues. Before winter while Koi can still eat, feed your Koi with medicated food one more time. If you do, please do so before 55–65 °F.

If you believe your Koi is sick, than refer to our article on Koi diseases, symptoms, treatments, and tips for how to know if your Koi is sick.

4 Methods – How to Winterize Pond for Fall and Winter

There are several ways to winterize your pond and Koi. Depending on your pond situation you may choose to keep your Koi in the pond, move some or all to an enclosed holding tank or build a greenhouse around your pond. These are the 4 winter Koi care methods we recommend for you to consider.

1. Keep your koi in the pond for Winter

This is probably what most of you do, especially if you live where it snows and freezes a pond over. Use these tips for success.

In this case, please do the following:

  • Stop the water pump and filter. If you have multiple pumps, you may not have to stop them all, but make sure water does not move and push Koi too much. Let them hibernate calmly. If you stop filters, please drain all water. If you leave water in them, they will hold rotten, sludge water until spring. You do not want that water going back to your pond.
  • Keep an air pump running. The air pump will keep a hole on the ice. It will de-gas your pond and also prevent ice to completely freeze your pond and for degassing.

2. Move koi to a holding tank inside a garage or enclosed space

Once Koi enter hibernation, especially underneath ice, you have no idea what is happening below. Sometimes this is not realistic if you have a large amount of Koi in your pond. Time to think like local interior designers and find a beautiful place for your koi’s indoor home

For piece of mind, it is a good idea to set up a holding tank in a garage ideally with a Koi heater. You can learn how to create a Koi quarantine tank in this article.

Buy 300 Gal. Tank to quarantine and house your Koi

Buy Therma Koi Heater to warm your pond

Buy 1000 Watt Titanium Heater and Controller to read temperatures easily.

If they are small enough and not many, bringing Koi inside for the winter is an option; or you can bring in only your favorite ones. This way you can monitor and enjoy your favorite Koi during winter.

If you can set your water temperature at 50 °F+, you can feed them Manda Fu. If you are able to set higher temps, you can feed them regularly. When you feed them, please do not forget to install and run a water filter, too.


3. Build a greenhouse to cover your pond

You can buy a small greenhouse kit to cover your Koi pond in winter. Or you can build frames with PVC or wood and put plastic sheet over them. This way, you are not worrying about your pond freezing over.

In this method, you can often visit your pond and check your Koi. If you can install a heater, you can even grow your Koi like all year around like you do in the summer months.

Use a plastic sheet to cover your pond frame and hold it down with heavy objects around the outside. In the photos below you can see an example of how one of our customers built a frame that can be used for both shade and as a support for the Koi pond winter cover. There are many ways to accomplish this greenhouse Koi pond style and with a little creativity you can build one to keep the warm air inside with your Koi. Don’t forget the value of a Koi heater!

Example of pond before prepping for fall and winter (photo by customer Val Loh).

After pond preparation with a plastic sheet covering (photo by customer Val Loh).

4. Cover your pond with solar cover used for pools

  • Start by laying rocks, pipes, or lumbers such as 4”x 4” across the pond in 1-2 feet apart.
  • Then, put solar cover over being held down by the weighted objects.
  • Ensure the entire pond is covered.
  • Keep your air pump running to de-gas and prevent pond from completely freezing.

Q&A to Prepare Koi Pond for Winter Survival

Learn from Taro Kodama as he explains further on how to create a winter pond where your Koi will survive the cold. Use the tips in this guide to care for your Koi through the fall and winter.


Can koi fish survive winter in outdoor pond?

Yes, they are able to survive. Follow the directions above in this article to winterize your pond.


Should I stop pond waterfall during winter?

Yes. even if you put up a greenhouse, the waterfall will expose water to cold air and chill your pond water. We recommend you stop or bypass the waterfall for your pond during the winter.


How deep should a koi pond be for winter?

The deeper the Koi pond is, the better, especially where it freezes. Five feet ideally is what to shoot for, but I know customers who have only 3 feet and do ok with Koi winter survival.


Should I drain my pond in the winter?

If Koi are relocated to an indoor tank or a different tank, then I don’t think the pond needs to be drained. In spring before you move Koi back, the pond should be drained for the new season.


Can koi fish freeze and live?

If a Koi is frozen in ice, then it will not survive the winter. Using winter Koi care, you will prevent your Koi pond from freezing the Koi; and thus they will survive the winter. We recommend using a Koi heater if you are in a cold environment.


Should I cover my pond in winter?

It is recommended that you cover your Koi pond in the winter to keep the water warm and keep leaves/debris off the pond. There are 3 recommended models you should follow for your pond in winter.


Do koi fish eat in the winter?

Koi can eat in the winter, but cannot digest food. So when it is under 50° F, we should NOT feed Koi. With Manda Fu Koi food, you are able to feed Koi fish down to 45° F.


Do koi grow in the winter?

If the Koi do not eat, then they do not grow. We recommend using Manda Fu in the fall / winter months due to its increased digestibility.

Good Luck in your Winter Pond Care!

Comment below if you have any more questions.

Winter pond care is all about ensuring a healthy start to the next season, so take the time and make sure you are providing an environment that fosters a strong immune system to benefit you and your Koi.

Remember that an ounce of prevention is worth a pound of cure!


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In the comments, tell us how you winterize your pond for fall and winter…