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 view more of our Koi for sale.
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:
- Keep your koi in the pond for Winter
- Move koi to a holding tank inside a garage or enclosed space
- Build a greenhouse to cover your pond
- 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
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.
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.
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.
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!
Kodama Recommended Products
- 300 Gal. Tank
- Therma Koi Heater
- 1000 Watt Titanium Heater and Controller
- Manda Fu Food
- Water Filter
- Pond Thermometer
- Koi Prazi
- Ich-X water treatment or a similar product such as Terminate.
- Make your own medicated food with antibiotics
In the comments, tell us how you winterize your pond for fall and winter…
Thank you for taking the time to publish this article I am sure it will be very helpful to some. I have a 2500 gal pond that is 3′ at the deep end I lay pipes spaced about a foot apart over the pond and about 1′ above the water surface and very little sun hits my pond in the winter an it usually will not freeze over as long as the edges of the plastic are held down with rocks. I live in Pa where it can get down to zero degrees. I think this is very important and also get all the leaves out before hard winter sets in.
Thank you so much for sharing your methods. I am sure it is helpful for the others too.
I have 4 6-8″ koi that remained when I got rid of my large pond. I would love to keep them. They have spent the past year in a horse trough with greens, not being fed. I will need to ship them from Carmel, California to Charlottesville, Virginia. I can have them in an indoor aquarium or plan for something on a deck. I need help. I hate to leave or lose them.
So you need to know how to transport your koi?
Do you still need to rehome them
I bought two 3 inch Chinese HiFin Banded Sharks for my 4000gal pond. They are supposed to be great algae eaters. They survived through our relatively mild Winter here in eastern Washington State until late January. I don’t see them now. If they have died, I suspect it’s because of the lack of algae in the pond and not cold water. Of course I don’t feed the koi when water temps fall below 50 degrees.
What are your thoughts about the Chinese fish and their probable demise?
I am very sorry. I do not know much about these fish.
Our Koi are in a natural pond with frogs, leeches, and insects. We can stop them from eatting in winter and the pond is too big to cover or catch them We live in Canada, any tip for over wintering?
I have never herd of ich-X before
I’m curious can this be used with sensitive species? Sturgeon ?
I have a Koi pond that is 38” deep. We do minimal for our pond in the winter here in Colorado where it can get to -20^.
I typically run air pumps to add air to the water and I keep my main waterfall running to ensure adequate aeration. It will usually freeze completely over the waterfall during Jan-feb but otherwise runs continuously. My Koi – 10” – 28” have done quite well during the winter hibernating on the bottom for the last 10-12 years. I do not feed the fish during the winter, if they need food they can find adequate supplies in the pond itself.
Thanks for the site, it is very informative.
Great practice. Thank you for reading our blog and leaving your comments.
I live in Colorado at close to 8000′ above sea level. I have a pond, just built this year, with a skimmer and a waterfall that is around 4000 gallons. We have 12 goldfish living in it and will overwinter. I keep getting conflicting information; I prepped the pond for winter by removing the pump and shutting down the skimmer and waterfall. I dropped the water level below the skimmer opening and installed an aerator for a 5000 gallon pond. Trimmed and sunk below what I hope to be ice level. But, my pond has completely frozen over and it’s only December. I called the aerator company and they state that the waterfall and skimmer should be left on year round! I do NOT know what to do- the pond is frozen so I can’t really start the waterfall again and there is BIG concern that the pump and water lines will freeze. Also, concerned with depth of ice and if the fish will survive (we already have dead frogs and that’s another challenge to figure out) and we dug it about two feet deeper than the pond kit company said it needed to be; thank goodness since we had to drop it a foot to get below the skimmer opening. I am at a loss of what to do and any recommendations or ideas would be GREATLY appreciated. TIA!
Hi Laura, I have had koi pond for very twenty years in Missouri.I shut my waterfall down when it got below 40, kept the aerator going and put two tank warmer’s in so as to if it was below freezing they would kick on.I never had a problem as long as there were place on the pond that didn’t freeze over from the tank warmer’s. I now live in Florida and brought some of my koi with me. I hope I was of some help.
Once last thing to my massive post- the aerator company said that the ammonia levels and such from the fish would build up and kill the fish if the skimmer/filtration was turned off… HELP! TIA 🙂
I am very sorry for the late reply. It is probably the best to contact your local pond person. If you live in Colorado, try professional Ponds ( https://www.professionalponds.com/ )
Hello I inherited a very large KOI pond its about 15 ft x4 ft..with about 30-40 fish! How do you inherit a KOI pond, well the previous home owner lived until he was 97, and passed away. I bought his house including the ponds. I am a single mom..my kids just left the nest last year..and I am an animal lover. I hope I do right by these fish but I am probably going to need tons of learning and help!
Koi is a great hobby and I am sure you enjoy them. If there are any we can help you, simply email us at firstname.lastname@example.org
I have a 14×20 pond 2.5 deep in the deep end. I usually run the pump all winter with a 2500 watt tank heater in the deep end and 3 or 4 air stones to keep holes open.Which has worked well in the past. my new quandary is my frog has taken to hibernate in my bio falls,
do you think he will survive the winter there? I have a 2 1/2 inch insulation over the top.
do you think he will surviveGeorgeG there ?
Hello, I am sorry I am not really familiar with frog hibernation. I assume if the environment is good for Koi, it should for frogs, too. But I am not sure. Can anybody answer?
I have lots of Frogs. Which = tadpoles = food. After the ice melts & temperatures with sunny days warm the banks. The frogs & tadpoles appear, about 5 warm days (50’s) later my fish will swim to the banks & start chowing down. They must wake up to eat?
I have secured tarpaulin sheets onto my pergola, all the way round, to keep the cold easterly winds at bay. Currently i have a pond water temp of 4.1c, i hope tonights forecast of -11c doesnt have an adverse effect.
My wife and I live in north central Florida.
Our pond is 7 ft deep.
They were 8 to 10 inches long when they went dormant.
We have yet to see them this year ?
All the bluegills,brim we are seeing.
But yet no catfish or koi.
Any ideas ?
Thanks for sharing this! I was really worried about my Pond coming into the winter season. The contractor of pond kits near me here in Colorado, also gave some great advise so I was able to winterize my Pond. Thanks to you guys and my contractor!
Can you please let me know why one of my large Koi has appeared at the surface of the water. Is he at the end of his life – can I do anything to help him?
This can happen due to a number of reasons. Please send our customer service team a picture/ video by email and we can further help.
This may sound silly, but it has worked for 9 out of 11 fish over the years. I have about 30 fish in my pond, ranging from 6″ to 20″ goldfish & koi. When i see any of my fish start to float on their side or belly up, i get a piece of netting about the size of the fish & fill a tank that the fish will fit in, & i wrap the netting underneath the fish like a sling. The fis has to be snug enough to hold the weak fish in one position (right side up), but loose enough for the fish to wiggle out of when & if he gathers his strenth. The i put the fish in the tank next to the glass & clip the top of the sling with clothes pins to the top of the tank. The tank has to be filled to the top so it covers the snugly wraped fish. Keep an eye on it for a couple days. If it looks like he is turning over, straighten him out & re clip it. This gives them time to build up their strenth, instead of struggling to keep from dying. Like i said, it has worked with 9 out of 11 fish ive done this way. I know it sound ridiculous, but it works.
Thanks for sharing that sling method. I have had several fish with swim bladder issues, have given magnesium salt baths and held them upright for a brief periods, but no successful cures. Will give it a try.
I’m not sure if I should feed my Koi Hikari wheat germ in the temperature fluctuating from 50 to 70 degrees in Charlotte N.C. for about couple of weeks now. The Kois are so active and I’m very attempted to feed them. What do you recommend and is it ok to feed them in mild Winter temperature? Thanks in advance and I look forward to hearing from you soon.
It is ok to feed them if the temperature is over 55 degrees, please see our kodama blog post on getting koi ready for winter.
Hello! Very informative site. Thank you for sharing your knowledge. My question is: I have approximately 50 fish in a 16’x20′ pond that is approximately 4.5′ deep. I have lots of filtration, air pumps, and water flow going due to accommodating the overload of koi. The temperatures have dropped to 20 degrees here in the Midwest, and I am fearful to turn all those devices off because of the overload becoming toxic at the bottom of the pond due to waste from the fish and other organic material that may not have filtered out and has now settled on the bottom of the pond (leaves, sticks, etc). Just this week I had two fish come to the top either upside down or on their sides. I have since put them in a quarantine tank and as of today they are doing somewhat better with treatment. Is it really okay to turn everything off except the air pumps that will leave a hole in the ice? Just really scary for me to just turn it all off.