WHAT HAPPENS TO POND FISH IN WINTER?

By: admin | Posted On: January 25th, 2011 | 37 Comments | In: POND FISH, Winterization

koi-under-ice

The warm weather is obviously the best time to be able to enjoy pond fish keeping. During this time pond fish and koi are active, lively, and highly visible. Many pond fish and koi become downright interactive with their keepers and will follow them around the pond, stick their faces out of the water or practically climb out of the pond to celebrate feeding time. During this time we all know exactly what is going on with our fish and all it takes is a quick peek into the pond.
Then the cold weather sets in and we slowly lose our ability to see what’s happening with our pond fish. Their activity slows down, they tend to keep themselves concealed, and once the ice and snow come; well, we lose touch with our fish. So what’s going on underneath those layers of ice and snow? What are our fish up to?
In short our fish are not up to too much. But pond fish not being up to too much is an interesting behavior all the same, given that they are so lively throughout the rest of the year. Koi and pond fish are poikilothermic animals, a fancy way of saying cold-blooded. This basically means that their body temperature is regulated by the surrounding temperature of the water, and their body functions respond and change according to the water temperature. The activity and metabolism of koi and pond fish is greatly reduced which is why they do not feed during the cold periods. Many experts say that because koi and pond fish are cold water fish they actually benefit from a cold period, however; prolonged cold spells are not good for them, they run the risk of their immune systems actually shutting down.
So what do they do? For the most part they sit on the bottom of the pond in the “warmest” pocket of water they can find. During winter months the warmer water is on the bottom of the pond as opposed to warmer months when the warmer water is at the top of the pond. I have often seen my koi lined up next to each other, facing the same direction as if they were in a parking lot! This is funny behavior that may lead to think that they are huddled together to share body heat; but since koi are poikilothermic that would not make sense, so this behavior is probably a way to fit as many koi into that pocket of warm water as possible. In larger warm areas you’d probably see a more random formation of the koi, some facing this way and others facing that way.
What happens to the koi and other pond fish is that they go into a state of torpor. Torpor is not quite full hibernation, because it is of a shorter duration than hibernation, but otherwise it is a very similar state of being: reduced body temperature, slowed metabolism, slow reaction times, reduced breathing rate and primary body functions. Torpor allows the animal to save the energy that would otherwise be needed for higher levels of activity. Because of the state of being in torpor it is a very good idea to keep things as calm as possible around the pond. If you need to open the ice in the pond find a quiet way to do it like using boiling water to open a hole, don’t chop it open with a pick ax! Even using a hand held drill with a hole saw is actually pretty quiet compared to other methods, and if the ice is too thick to open with boiling water the hole saw is a great tool to have. To maintain an open area in the ice try using a floating de-icer or an aerator. This open area in the ice will allow noxious gases, like ammonia, to escape from the pond.
Some people add salt to their ponds. I personally am not a practitioner of adding salt unless it is for treatment purposes, but if you do add salt to your pond you should dilute your salt levels during cold winter months. The salt can make your pond water’s freezing point drop to below 30F which will kill your fish. Generally speaking you should not let your pond water’s temperature drop below 34F. Temperatures below 34F will allow ice crystals to form on the gills of your koi, which can kill them, so watch the temperatures if you live in an area of extreme winter temperatures.
If your pond is cleaned and prepped prior to those cold dark winter months, then worry not, your koi and pond fish should do just fine. Like was mentioned the koi, goldfish, and pond fish in your pond do not DO much during the winter months. Spring will be here soon enough and your fish will start again with their antics and amusing behavior. But for now you have a better idea of what is happening out there under the ice and snow, and you are not missing out on any party. If only we could share that state of torpor and wake again when the spring has sprung!
The LOVE YOUR POND blog is written by Mike Gannon of Full Service Aquatics. Mike is a professional pond builder and expert in the broad topics of fishkeeping and water gardening. Mike also produces THE POND HUNTER video series which can be viewed on Youtube. “In The Pursuit Of All Things Aquatic” the Pond Hunter videos provide how-to pond construction videos, pondumentaries, and videos of related interest. Mike resides in Summit, New Jersey with his wife and 2 daughters. To visit his website go to www.loveyourpond.com and visit The Pond Hunter at www.youtube.com/thepondhunter. All copyrights to this material belong to Mike Gannon.

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  1. Eleanor Says:

    on February 23, 2013 at 9:42 am

    Hi, is the image ‘koi-under-ice’ copyrighted? I am aking as I am doing a koi fish project and we can only use copyright free images.
    Thank you
    Eleanor

  2. Mgannon Says:

    on March 2, 2013 at 3:57 pm

    Hello Eleanor, that photo is not likely copyrighted. I too try to use non copyright images, but I’d doa google search just to be sure!! thanks for reading the blog. Mike

  3. Ginger Says:

    on September 2, 2013 at 9:59 pm

    Hello Mike,
    Someone gave my son pond fish as a present, and because we are renting at the place we are living, there is no space for the pond fish to be inside in a tank. So, I have an idea of using a large planter that is approximately 40″ (plus) diameter to use as an above ground pond. Would a planter serve as an adequate pond for pond fish?

  4. Mgannon Says:

    on September 3, 2013 at 1:44 pm

    Hello Ginger,
    Thanks for getting in touch! Before saying that the planter will work, it needs to be considered what material the planter is made of. What type of pond fish are we talking about? What type of climate do you live in and will this be a year round housing for the fish? I have seen many patio ponds that have fish in them but cannot function year round because of cold weather conditions, or even very hot conditions. In all I’d say it is not the most ideal situation for fish keeping, but not impossible either as long as the conditions are right.
    Mike

  5. Karen Says:

    on September 9, 2013 at 9:47 pm

    I am a biology teacher considering an environmental club project to remediate an algae filled pond in a local park (central NJ) by seeding with duckweed and using Koi to feed on it. Do you think koi are hardy enough to survive winters here untended? I don’t know how deep it is, but that is one of the things the kids can investigate, I would be very grateful if you could give me some pointers.

  6. Mgannon Says:

    on September 10, 2013 at 12:47 am

    Hello Karen, that sounds like a great project. I’d need a bit more info to give you good advice, but generally speaking the koi will be winter hardy. Feel free to give me a call, I am also based in NJ and would love to discuss your project. Call Mike at 908 277 6000!

  7. Eve Brady Says:

    on September 10, 2013 at 9:52 am

    Hello,

    I have a pond which is very deep (about 4 ft) but last year in Norfolk it was so very cold and in the early spring two of my lovely fish died, they were quite old though so I am not sure f they simply reached the end of their life or died because they just couldn’t cope with the freezing temperatures. They have lots of shelter as I have used square sley type material drain pipes …(have used them for year and the fish love to hide in them and swim through them!) The water never completely freezes over as I keep the pump running which powers the water fall too so there are always two areas which are ice free, I am however still a bit concerned about the winter months this year, should I cover part of the pond with bubble wrap or something similar to maintain an element of heat?

    Looking forward to hearing from you,

    Kind regards,

    Eve

  8. Mgannon Says:

    on September 10, 2013 at 2:09 pm

    Hi Eve, I don’t think that it is necessarily an issue of higher winter temps that you need to have. I think with typical de-icer/aerator equipment during winter you should do just fine; and the many years of trouble free winters would support that. I cannot say why your fish passed but I don’t see reason to insulate the pond any more. Be sure you give your pond and filters a good cleaning before winter hits, and add more aeration if you need it! Mike

  9. Brittany Says:

    on September 23, 2013 at 2:43 pm

    we recently bought a house, and in the backyard there is a koi pond and there are maybe 10-15 fish in the pond. i’ve been reading on what i should do, but i’m still not 100% on what steps i need to take to get it ready for cold weather. it has a waterfall and a hand built filter system. i do have a heating rock to put in the pond. i wasn’t sure if there were any chemicals or anything like that that i needed to put into the pond. i know that they can survive the winter if the pond is prep properly. wondering if you can give me some helpful hints.

    thanks so much
    brittany

  10. Mgannon Says:

    on September 25, 2013 at 1:52 am

    Hey Brittany,
    thanks for getting in touch! Some systems can run year round, others need to be shut down. You can use cold weather food for your fish and feed until late October typically, and you can also use a cold water beneficial bacteria treatment during winter months. If you search on the LOVEYOURPOND blog a bit you will find tons fo great info on how to handle your pond during the winter and how to prepare your pond for those winter months too. Try using the search function for what ever questions you may have and you’ll likely find an answer! Thanks Mike

  11. Mike Says:

    on October 21, 2013 at 8:20 pm

    Hi I live in California and the current temperature is about 82 degrees. I cleaned my koi pond and I think I may have inadvertently woken the koi from their Torpor state. The koi are back in the cleaner pond but are all at the bottoms and lifeless. I can’t tell whether they are hibernating or dead :( . Any way to tell if I am an accidental mass murderer or not?

  12. Mgannon Says:

    on October 22, 2013 at 7:03 pm

    I am hoping for the best for your fish Mike. It should not take too long to know if they are dead or not unfortunately. If the temperature is 82 however; I don’t think your fish would be in a state of torpor. Hoping for the best! Mike

  13. Dave Says:

    on October 22, 2013 at 8:26 pm

    I have a small pond in Wisconsin. It’s about 3 ft in diameter, and 20 in deep at deepest. It has hardy lillies, and 3 goldfish – each about 3-4 inches long. I was going to bring the fish in for the winter and keep them each in a fishbowl. Problem is I can’t find them to move them to a fishbowl. Water is getting colder – I estimate it to be between 40 and 50. I’m afraid to leave them all winter, as the pond may freeze solid except for the deepest which may not be enough water to sustain them.

  14. Mgannon Says:

    on October 22, 2013 at 10:46 pm

    Hey Dave, it can get pretty cold in your area. I’d recommend trying to bring in the fish for the winter based on the size of the pond that you are describing. If you can’t then its a good idea to put in a de-icer or aerator. Let me know how you do! Mike

  15. Scott Says:

    on November 6, 2013 at 3:16 am

    I live in Central Wisconsin with a 150 to 200 gallon pond, with a depth of 19 inches. Should I try to heat and aerate this pond, to over winter the fish? Thanks, Scott.

  16. Scott Huntley Says:

    on November 7, 2013 at 1:51 am

    We have 150 to 200 gallon Koi pond about 19 inches deep and live in Central Wisconsin. Should I spend time and efforts trying to over winter my koi or will my pond still freeze solid?

  17. crystal Says:

    on November 7, 2013 at 10:06 am

    we took our fish out our pond and put them into fish tank into are house for the winter but they’re slowly dying did we take them out too late we had our first snow storm the snow melted and thenwe put in our house in the fish tankdo they need bubbleshopefully you get back to me as soon as you can so I know if we did something wrong before they all die my little girls are sad about it

    Thank you crystal j

  18. Mgannon Says:

    on November 12, 2013 at 10:27 pm

    Hey Scott, yes I’d recommend aerating and de-icing your pond during the winter months. Mike

  19. Mgannon Says:

    on November 12, 2013 at 10:29 pm

    Hi Crystal, I’m sorry to hear that you lost fish. I don’t think that bringing your fish in would have made them die unless they were not acclimated correctly. I am guessing that perhaps there was an ammonia spike in the new water and that may have killed your fish, but I am only guessing because there is alot I don’t know about the situation. Sorry again! Mike

  20. Dallas Clark Says:

    on November 23, 2013 at 12:23 am

    Question:
    My 2800 gal pond with waterfall with 14″ curtain pushing only 2000 GPH pump and my water is getting a white tent like an algae bloom in this cold weather, filters are clean, but, with a little sludge on the bottom (got behind due to wife on HOSPICE) Have 8 Koi about 7-8″, all readings seems A -OK or within range. Have been a Koi Keeper for 3 years
    and lost two beautiful Koi today. White tent of water is telling me what?
    KoiWrangler, Dallas

  21. Lydia Says:

    on December 10, 2013 at 7:03 pm

    I live in Danville, CA and this winter is unusual here in the SF Bay inland suburb temp has fallen to 20 degree F for a few days now. I see their gills moving. The two oldest are at least 30 years old, I inherited them 12 years ago and the prior owner could not recall exactly when he put in the pond so this is the estimate; they were elderly and he said they can live to 100 years! They are huddled together; they always hang out together like a married couple and sleep next to each other their “snouts” inside the where the UV filter is.. One of the larger ones that is by itself and is about 5 years old and almost matches them in size already black and orange with fancy tail – obviously I am no expert! I also have smaller ones that I received as a gift from the person who used to service my pond before he moved to Florida. This cold snap has lasted so far 5 nights with last night being the coldest and will probably last another two then go back to the 60s in the day. The water has a lot of foam but no ice. Is there anything that I should do? The waterfall is running. I have not fed them in a week. I typically feed them once week in the winter here.a small quantity of food. I was told to change the UV lights every other year. I do not have a new koi pond person He cleaned out and drained the pond every year and scrubbed it. I doubt most people will do that. What is the typical maintenance routine and charge? I have a pond filter, modern. that he installed a few years ago and a waterfall that is currently running. Basically I buy shrimp meal food from an installer of koi ponds from Southern California in bulk that i met on eBay for a very good price I have about 11 fish now. When I got the pond with the house in 1999 there were 40 fish including gold fish but something happened insecticide by a careless gardner not sure so only the largest two survived. a very sad day. I bought the one I described I call Barbie because it is so beautiful from Hawaii during the recession and one from North Carolina that really looked like common carp that died and grew so fast just one day floated to the top I thought that koi floated to the top when dead not stayed at the bottom. All those that died were at the top so I was surprised that you told the other California person that he would find if the fish at the bottom were dead. I have seen 38 die excluding Mr. North Carolina. One thing I learned is that when we had an island in the middle we could not have small koi the birds ate them and Loi the person who took such good care of my pond told me to remove it because the birds may have used it to “fish” and sure enough, after that for the first time I had small fish that survived! One time I was surprised to see a stork on my pond at 6 :AM that must have escaped from the Oakland Zoo. I thought a small aircraft was over my pond and I screamed! Since they are only in the Gulf of Mexico, it must have come from the zoo! Luckily I saw it.

    The former owner had blocks of salt that they used for the Koi and all sorts of medicine but none of that has been necessary. Any comments would be appreciated since I am not expert but am quite fond of my fish. I work out of my house and they take me outside. I pull out the leaves manually and spend some time out there and also clean out the filter rinse, backwash at least once a week. Anything else I should be doing? We have algae now., more than before on the rocks. I hate using the chemicals the fish do not appear to like them.

  22. Grace Says:

    on January 2, 2014 at 1:50 pm

    I have a 250 gal pond I put a few goldfish in. Every year the resident hawk gets them. My last set has lasted almost 3 years! Yeah. It is January in Atlanta and cold, not freezing. Currently one of the large fish is lying on the bottom looking dead. I went to remove him and he moved. I figured he is a goner. Then, 3 days later, he hadn’t moved and is on the bottom under some leaves. I went to remove him again, yikes, still alive. I guess he might live, I thought it was a swim bladder issue. this behavior is bizarre and no where on the web can I find this as normal. They have 14 babies I plan to give away this spring to the local kids. Too many fish for this pond. Thanks for the article.

  23. Mark Says:

    on March 25, 2014 at 12:16 am

    Hi, I moved into an old home approximately one year ago and inherited a pond with three koi and three goldfish. Since then my wife and I have done everything we thought possible to keep our pond healthy (we have a filtration system, pump, waterfall, we purchased a new deicer, feed them above 45º-50º, add small amounts of PH balance occasionally, etc) but unfortunately two of the three koi died within one day of each other this February. The third one is currently lying on its side and it looks like he’s not going to make it either. Several days ago I thought it was dead but when I went to lift him out with the net he flapped slightly. I went back again this afternoon and it appears to still be hanging on. I’m scratching my head over this because the three goldfish appear to be doing well.

    I have a few questions:
    1. Is my fish dying or is it hibernating? It doesn’t appear to be hibernating/sleeping since it’s on it’s side and very weak when it flapped.
    2. Is there anything I can do to help bring it back to health?

    Please let me know. Thanks.

  24. Mike Gannon Says:

    on March 25, 2014 at 10:21 pm

    Hello, thanks for getting in touch. I’m very sorry to hear about your fish loss. The remaining koi sounds like it is in a state of stress, not hibernation (or torpor, as it is called with fish!) The smaller fish may not be stressed mostly because their body mass is much smaller and changes in environmental conditions are tolerated better. It is very difficult for me to say exactly why you lost your fish without alot more information; however since you are a new pond owner you should know that fish loss is not a typical problem. I believe it must be an environmental issue given the proximity in time that the other fish had died, and probably not necessarily disease related.
    I would add a bit of pond salt to a therapeutic level, which is about 1/2# salt per 100 gallons. You can use solar salt that is also used for water softeners to save a bit of money, or just buy “pond salt” its the same thing. Also add some additional aeration, then wait and see how the koi does. Don’t bother it or poke at it, just give it time; it will either recover slowly or …not.
    Good luck, and if you need anything else just let me know!
    Mike

  25. Mark Says:

    on April 1, 2014 at 3:13 am

    Thank you Mike for your reply. This is very helpful to read. Sadly, all three koi were lost. Your tips are useful regardless. We’ll know for next time and hopefully be better prepared.

    -mark-

  26. Protecting Your Pond In The Winter | All Pond Solutions | All Pond Solutions Blog Says:

    on April 28, 2014 at 3:28 pm

    [...] Pond fish virtually hibernate in the winter months because their metabolism is controlled by the temperature of the water. This means that you should start reducing the amount of food they are given as the weather gets colder. You can stop feeding them completely when the temperature drops below 4oC. [...]

  27. Mike Gannon Says:

    on May 11, 2014 at 3:44 pm

    Hey, thanks for the comment!

  28. joyce jones Says:

    on September 23, 2014 at 6:11 pm

    Hi, I have 4 very small koi fish ( about 4 inches) for a couple of months and they seemed to be doing well – the the weather dropped sharply (late sept.) and they have disappeared and are not eating – it is only about 55 degrees here in wash. d.c. , do you think that they are just getting ready for winter and—will they make it is about 5ft. x 3 ft. above ground cement pond – there is prob- thanks ably about 20 inches deep water

  29. Mike Gannon Says:

    on September 23, 2014 at 11:58 pm

    Hello Joyce,
    above ground ponds do tend to have some issues when it comes to temperature control and they get pretty cold. Typically at 55F or less fish will stop eating or have very decreased appetites so given the water temps I am not surprised they do not want to eat. If we get any more warm spells offer them a bit of food and by November your feeding will mostly stop until spring. -Mike

  30. Anna Says:

    on October 6, 2014 at 10:12 pm

    Hello,
    I live in Albany, NY and have a pond that is 2 ft deep. I have one goldfish that I put in this summer. He’s gotten bigger and seems to be doing well. Do I need to bring him in for the winter, given the shallow depth of the water? The pond is roughly 5 ft long, 2-3 ft wide and again, 2 ft deep. Thanks in advance!

  31. Mike Gannon Says:

    on October 8, 2014 at 1:57 pm

    Hi Anna, in general 2 ft is a sufficient depth to overwinter your fish outdoors. All of the ponds we build are at least 2ft deep for that reason. In extreme weather, like extended periods of time in single digit cold weather, you need to be careful. you should always add a de-icer for the winter months and an aerator will go a long way to ensure your fish do well during the colder months. Thanks for reading and commenting! -Mike

  32. Eli Says:

    on November 3, 2014 at 12:37 pm

    Dear Mike,

    My name is Eli and I reside in Philadelphia, PA. This Spring we installed one of those premade plastic black ponds. Its on the small scale I would say more like the size of a bathtub. Not sure exactly how many gallons, maybe 60??? Anyway, we got some tiny and relatively small pond fish there that were thriving finally in the past few months. Its already brutally cold and windy here (especially yesterday) but although its already November Philly is expecting a climb of temperatures that will reach the 60′s and maybe even the low 70′s but I expect it to be isolated and more rare occurance. It is more than likely that we will see a steady drop of temperatures to below freezing and that snow and ice will come out way for prolonged period of time. Last winter (2013 into 2014) was very brutal so much so that the three hardy windmill palms I ordered from Florida seem dead as new frons did not form and all we got is the trunk, which I still refuse to dig out (I would appreciate advise w that, if you know anything). The special salt we added during the summer and fall once a month did not change anything for these poor three once beautiful 5 to 6 feet so called hardy palms that cost too much money I barely had)-; Anyhow, so I don’t want something similar to happen to my beautiful pond fish. I have a pump inside the water and a filter w UV light stationed just outside the pond both connected to an electric outlet. The waterfall seem to be very slow compare to before. I thought maybe because they fall on stones we put and don’t splash the pond itself from high above… or perhaps its an issue w the filter needing some cleaning, although it is new and installed in late summer, I would say. We took the pump out one day and applied water to its holes with pressure in order to “clean” it outside the pond. Then we placed it back. The waterfall we shut every evening since the spring or summer when it began working with this new pond. It is surrounded by rocks and special plants all around. In the water there is green submerged plant I bought at the pet store. Hopefully it will survive the winter though the bamboo we will probably take indoors. In the morning, we use the remote control to restart the waterfall. We collect rainwater which we add to the pond whenever it loses water. Sometimes days and weeks go by without major water lose, but one time we had 70% of the water suddenly gone. It scares me, and I wonder if its possible that all the water will be lost during the winter, and if we should add more water during the winter. Also, if temp will be in the 60′s or 70′s again, should we feed them. We have not stopped the feeding yet though during cold days the fish swim below and mostly inactive. We do not have a deicer yet and debating between getting a reasonably priced Deicer on ebay or removing the fish from the water, and possibly emptying the pond from water and placing them into a large plastic container like those used by the municipality for recycling trash. Sadly so we don’t have an aquarium); Should we keep them outdoors or indoors in your opinion? If indoors, is the cold and mostly dark basement a good place or some place else? Should we feed them every day indoors as if it was summertime outside, during the winter months? And do we need to buy anything that would do the job of a pump and filter? or can we just have them in the container and just maybe replace the water every now and then. As far as the pump and filter that are now outside, if we keep the fish outdoors during the winter should we have them both work together w the waterfall or should we disconnect the pump and filter and not have the waterfall work at all but only use deicer or hot water to break any potential ice as some have suggested here. I was told at a pond shop that the UV light should be brought together w the filter indoors and stored away in a relatively warm place during the winter months. Is that correct? If we will bring them in to that container I mentioned I suppose it only makes sense to bring the filter indoors and after cleaning it for next Spring to just store it somewhere, while leaving the pump disconnected or shut off during the winter months after removing all the water from the pond, right? I believe that removing it completely will be difficult due to the fact its connected with the waterfall through and under the rocks that surround the fishpond. Sorry for all the questions but please let me know about the indoors vs. outdoors and the situation with regard to the water, pump, filter, and waterfall. Americaeli@aol.com

  33. Mike Gannon Says:

    on November 4, 2014 at 9:54 pm

    Hello Eli,
    Thanks for getting in touch and checking out the blog! Based on the size of your pond, if it is easy enough and you have the room, then you may want ot just bring the fish indoors. If you plan to leave them outdoors then I highly recommend using a de-ice AND an aerator. A small pond like that will have a pretty tough time if we have another winter like last year! If you bring them indoors, the basement should be fine but give them some sort of light source so its not too dark for too long. Feed them, but feed them lightly since the water temperatures will still be low. Check the water temperatures and feed you fish based on the temperature. 55F and higher they need to be fed. I don’t have a great solution for your palms, sorry, but they are great plants!
    Thanks again, good luck, and let me know if I can help any more!
    Mike

  34. Julie Says:

    on November 30, 2014 at 5:35 am

    Hello ~
    This is our first winter with our beautiful koi pond and I am a nervous wreck. There are five koi and one goldfish in the pond. Here in Illinois we have had a sudden cold snap but I feel we prepared for it. We had the man who installed our pond come out and shut down the waterfall and disconnect the pump. We have a 300 watt deicer as well as an aeration unit in the pond. This afternoon I went outside with our dogs and walked over to the pond and saw our largest koi very close to the top with it’s head hidden under the rocks. His (or her) stomach looked very bloated/swollen. He appeared to be moving but very slowly. My husband gently touched the fish and he slowly swam back into their cave. I am worried he might be sick ~ I’m not sure what the swelling is and am hoping you might be able to provide me with some guidance. I am also curious if it is normal that I have not seen any of the other fish for several days now. The temperature was close to 50 today and I thought I might see them but have not ~ only the large one I described. Any advice you can provide would be much appreciated. My greatest concern is that I do everything to ensure they survive the winter season ahead. As a reference, our pond is 3 feet deep at the middle and 2 feet deep along the sides. Thank you.

  35. Mike Gannon Says:

    on November 30, 2014 at 6:04 pm

    Hi Julie,
    It sounds like the pond was shut down properly. I typically recommend along with the de-icer the use of an aerator for the pond as well. The aerator will help the fish more than just a de-icer. The bloating of the fish is hard to say exactly without seeing it (you’re welcome to send photos if you can get a good shot); however it could be dropsy if the scales are not sitting smoothly against the skin of the fish. However, what you described as the fish staying close to top and “hiding” its head suggests to me that it is sick… without knowing exactly what’s wrong I am not comfortable telling you to medicate, but the addition of some salt (solar salt) to the pond would be a safe measure to help control further issues. The rest of your fish hiding could be because it is cold and they are just not being active, the water temps are probably still lower even though the air temps are higher. BUT, since it seems that 1 fish is sick, I’d do the salt just to make sure the rest are not breaking out with something too.
    Mike

  36. Deanna Says:

    on December 13, 2014 at 7:06 pm

    Hi Mike:
    We took ownership of our home in October. It came with a water feature with 8 koi in the pond that is about 18 inches deep. The previous owners put it in and gave us minimal information. We live in Oregon and so the weather has been on again off again warm-cold-warm-cold. I’m not sure at all how this affects our koi. We have stopped feeding them because the water temp is below 50 degrees. But they are not in their “sleep” state either. We are not sure what to do about the koi at this point. How do we keep healthy koi in Oregon when the weather is not cold or warm?

  37. Mike Gannon Says:

    on December 15, 2014 at 9:08 pm

    Hi Deanna,
    What is most important to remember is that the water temperature is the deciding factor on when to start/stop feeding your fish. If water temps are staying less than 55F then you do not want to feed even if they are not fully “sleeping” yet. And of course you will not want to start feeding until the temperatures are consistently above 55F. Even if they take the food during lower water temperatures >55F, they will not digest it correctly and that is what can cause issues. Just be sure to have an aerator running to oxygenate and de-gas the water during winter, or at least a de-icer; BOTH preferably since your pond is on the shallow side. If the fish have done well through the winters in years past I would thing they will do fine moving forward, and there is little maintenance to do in the winter months for your fish. Hope all goes well! Mike

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