Blue Ridge Koi Blog

Posted by Casey LeFever



Koi and Winter Hibernation

Did you know that koi hibernate during the winter?  Yep, just like many other animals, koi are very sedentary during the fall and winter months.

Now, to be clear, koi do not technically "hibernate" during the winter.  And their activity is not like other hibernating animals.  There is no burrowing, no hoarding of food, no stealing of pic-a-nic baskets.  But they go into a hibernation-type state just the same.

When the water turns cold, you will notice a dramatic decrease in the activity level of your koi.  They will "sit" on the bottom of your pond, floating upright with their pectoral fins tucked up underneath the body.  Their heart rate and metabolism slows during the cold period. 

Check out this video clip of koi in cold fall water.  (Sorry in advance for the bad cell phone quality).  Notice that while some of the koi are still moving slowly about the pond floor, others are already sedentary, floating in place with their fins tucked.

Hibernating Koi in Cold Fall Season Water from Blue Ridge Fish Hatchery, Inc. on Vimeo.

Koi should not be fed (and in most cases will not eat) when the water gets below 50 degrees.  That's right, they don't need to eat at all.  Koi will go through your entire winter season without eating pellet food added to the pond.  

Although koi can live through the winter in a frozen-over mud pond, it is a good idea to keep at least a part of your pond's surface unfrozen.  The climate that you live in will determine what you need to do to prevent freezing.  In some warmer climates, keeping the water circulating constantly may be enough.  Colder climates might require a heater.

If you have any questions, look for a qualified koi and pond dealer in your area.  Someone local will be best equipped to answer your questions about koi and the cold winter season.



Apr. 13 - 2014

When does koi hibernation end?

    Casey LeFever
    Apr. 13 - 2014

    Hi Linda,
    Koi hibernation ends in the spring when the water begins to warm. When koi are coming out of their version of hibernation, you will see them become more active, coming to the surface of the water and eating.

Oct. 06 - 2014

What if a koi is pregnant going into the cold season in PA?

    Casey LeFever
    Oct. 07 - 2014

    Hi Jay. It is not likely that your fish is gravid (carrying eggs) at this time of year.

Oct. 08 - 2014

Casey, The fish looks fat from almost head to tail. It really looks stuffed. It looks nothing like the other fish in the pond and there are many. Thanks

Oct. 08 - 2014

Hi Casey. It sure seems like she might be. She looks fat from head to the rear fin. There are a lot of fish in there and I don’t thing she can compete with the other fish that much so that she would be that overweight. Interesting though thanks.

Nov. 08 - 2014

How can you tell which type of Koi you have (they were all in the big pond when we purchased it in 1997).. There were five now down to three (no idea what happened to the two). One darker orange and one lighter orange and one white. All about 18 inches minimum length.

    Casey LeFever
    Nov. 10 - 2014

    Hi Howard. There are multiple variety guides online that will help you to determine what variety of koi you have. Thanks.

Mark H
Nov. 13 - 2014


Nov. 15 - 2014

I put my Koi in a 5 foot square plastic container that is perforated with 2 inch holes for water circulation. Then I sink the plastic box in the lake in 8 feet of water.
I have done this for many years as soon as the water temp goes below 40 degrees.
I just put them in the lake in central Ontario Canada this past week.

Nov. 22 - 2014

Hi. I am fairly new to koi keeping. I have had my pond for just over a year and this will be the second winter. Last year I was unable to see my koi shortly after winterizing the pond as the water clouded up, so I only got to see a little glimpse of what they are like when they start hibernation. This season, the water is still crystal clear :-) and I can see them pretty well. I go out to check on them and they still make an effort to swim up to me. They also like to swim up to the shallow end of the pond at night and huddle together. They only go down to the 4 foot section during the day. I am wondering if all this activity is normal for their hibernation stage? The water temp is 37 degrees. I would think they would stay in the deep end …..????

    Casey LeFever
    Nov. 24 - 2014

    Yes, that activity is normal for koi during the cold winter months.

Dec. 07 - 2014

We have one of our koi about 6 years old 16 to 18 inches long acting different from the other 15 koi . They are all at the bottom of the pond where they are moving around some. He is on his side and back breathing shallow not like the others. He doesn’t look right. With the snow , ice and a long winter coming . My big fear is he is sick which is a sad thing but I don’t want to leave him in . I’m worried I might lose all the koi by next spring . We can get him out if we need to ,so we can protected the others!!

    Casey LeFever
    Dec. 10 - 2014

    Hi Nancy. Sorry to hear that. It would probably be best to remove that fish from the pond before it freezes over. Good luck.

Kevin Nichols
Jan. 10 - 2015

I have 3 koi 8 gold fish all goldfish are doing 2 koi acting very weird 1 floating appears to be gasping for air on top floating the other koi much larger on bottom of pond lying on side moving around a lot 1 koi seems unaffected by the cold and seems to be concerned for his fellow friends more than anything is this normal I have had fish for 2 years and take care of the water very well with proper water balance with pond products etc. have water features spitters ,eratores.sorry for my spelling I do have a heater but haven’t used it since fish didn’t seem to bothered last year water temp.39 and outside has been 50-60 days and sometimes high teens at night.

Jan. 26 - 2015