Frozen ponds is a subject that of course only seems to pop up seasonally, like during winter…well of course, why worry about it at any other time of year? The problem I see again and again with many pond owners is a real misunderstanding of what is happening with their ponds during this season, and if the subject is not addressed quickly the season ends and if a pond is not frozen why talk about it. So NOW is the perfect time. Here in the northeast U.S. I’d guess just about everyone’s ponds are frozen if they have not taken the steps to de-ice their ponds. So, naturally this is the time everyone goes into panic mode about what to do with their iced over pond.
Here is some, I hope, comforting information about frozen backyard fish ponds and watergardens. When a pond freezes over it forms what would best be described as an ice cap. This ice cap will generally extend from edge to edge of the pond, but it is not airtight and will still allow air flow. This seasonal stage of your pond can be very pretty and enjoyable IF you truly understand what is happening below that ice cap that is putting a barrier between you and your fish and plants.
The primary customer concern with freezing ponds is how the fish that are below that ice cap are dealing with it. I have yet to get a distress phone call from a customer about how the ice is affecting their water lily, after 15+ years in the pond industry that phone call has not yet come. The distress phone calls are always about how the ice is affecting the fish. On the assumption that your pond is: an in-ground pond, constructed properly to a depth of 30+ inches, and fairly well managed during the year and is not ice capped with loads of decaying leaves, debris, or putrefied food below it, the following information will apply.
Ponds freeze from the top down and RARELY freeze solid all the way through. Fish ABSOLUTELY DO NOT under any circumstances freeze into the ice and then thaw out during the spring to comeback to life. If a fish freezes it only has one outcome…death. I have customers swear their fish are frozen into the ice, but I personally assure all of you and them this is not the case. When you see a frozen pond it is only ice capped which will slow down the oxygen intake and ammonia release of the pond, but it does not stop it. In many ways a winter time ice cap for your pond is desirable. The ice cap on the pond does not actually even touch the water, and really acts as a fantastic form of protection from the harsh conditions of winter. Between the water and the ice is a pocket of air and below the air pocket is fresh unfrozen oxygen rich water. Very cold water carries large amounts of oxygen which our pond fish utilize during the frozen times and our aquatic plants still photosynthesize during the winter and create more oxygen for the fish.
Do not EVER try to walk on your frozen pond for the obvious safety reasons. It is a good idea, however; to keep the pond cleared off of snow, try to use a long handled broom to clear snow as the noise of shoveling can be a bit much for the dormant fish. We still want to let light into the pond for our aquatic plants to do what they need to do, create oxygen. Breaking a hole in the ice is not a good idea as it stresses the fish, try quietly melting a hole in the ice if you need to. Recent studies do relate that the amount of oxygen that diffuses into pond water during the winter is very minimal, so those de-icers and aerators we all hook up are doing more of a job of degassing the pond of ammonia build up, rather than oxygenating a pond and quite honestly the floating de-icers really don’t do too much at all. Studies have actually proven that ponds that are ice capped and have dormant aquatic plants will have a rise in oxygen levels if left undisturbed. The stirring or circulating of an ice capped ponds water is not really a good thing to do, unless it is a very dirty pond and an emergency situation is on hand, otherwise leave the pond water alone and let nature do her thing.
Pond aerators should be employed and placed into areas that maybe “dead zones” during the rest of the season. Aerators should keep an open area most of the time but even when they get frozen over and you have an “ice dome” those aerators are still degassing the pond and moving that pocket of air in between the pond water and the ice cap.
Fish will remain dormant, or in stupor mode, during this time and many fish experts agree that this dormant period, for koi especially, is important and koi have evolved to endure these conditions. At the end of winter when spring returns and we can start so see our fish again, the will surely be a bit thinner but that is normal and shows that they were able to handle the winter time and utilized the fat reserves they build up in preparation for the cold spells. It also gives you the opportunity to enjoy feeding them and getting nice and rotund again during the rest of the season.
Frozen ice capped ponds should be as relaxing to look at as your pond is at any other time of the year and hopefully with some of this information you can now rest easy and know that your fish will come through winter after winter without any issues. Keep nutrient load low, keep fish population controlled, provide a simple aerator, and don’t mess too much with your pond and you and your pond will be fine. It is a short seasonal period of freezing, enjoy the short lived beauty of an iced over pond because the spring will be here before you know it!
Great blog entry! This helps me be more comfortable with using my aerator as my de-icer which is a huge weight off my shoulders (and wallet!), THANKS!
I love all these self proclaimed aquatic experts. If you stayed awake during High School chemistry you would have learned Boyle’s law and would never make the inane statement that gasses wont diffuse into water at low temperatures. So much for the internet “experts”. Isn’t there anyone in the pond business that actually knows what they are talking about?
Hey Clueless, great name! I am not seeing where it was stated that “gasses won’t diffuse into water at low temperatures” in my blog post. Maybe before your start an angry rant you should make sure that your ranting at least has a basis to support your negative and incorrect criticism. THINK before your post these ridiculous rantings, and make absurd conclusions about peoples high school education that you know absolutely nothing about. High school was a long time ago for me, maybe you should move on too.
I live in upper New York. My 2 ponds are not huge or probably more than 24 to 30 inches deep. Each year as it gets cold I don the old wader boots, take out all my filters and pumps, clean and put back in ponds. I leave the pumps right below water level to keep small opening in ice when ponds freeze over. My fish all fare well and seem fine come spring. All my water lillies come back also.
Hey thanks for commenting! I am glad that your ponds do well each year. obviously you’re doing something right! I’d love to see some pictures. Visit me on Facebook too. http://www.facebook.com/loveyourpond http://www.facebook.com/mikegannon
I was wondering how long a pond can remain frozen over before it affects the fish? I read somewhere not to let it stay frozen over for more than 2 days. Year after year here in the northeast my pond at some point will freeze over and Im afraid to even let it close up at all. I currently use a pond heater along with acerator and the pond is 30″ + deep. Thanks much
Hi Cheryl, most ponds can stay frozen over for longer periods of time, but it is depending on the condition of the pond. If the pond was not well maintained it will be more of a risk. Also you should have an aerator and/or de-icer set up on your pond int he colder regions to make sure that there is an exchange of gases in and out of the pond. Looks like how you are set up should not be a problem if your pond is covered for extended periods of time. Thanks for reading and commenting, I love hearing from readers!
I just came across your blog because I Goggled covered ponds. I have had a pond for 10+ years increasing it in size several times. It has a max depth of 28 inches. I have only lost my fish one time over the winter as the liner failed and the water drained out under the ice cap. I have always kept a hole in the ice to release gases. This year I decided to cover my pond using PVC pipe, insulating foam board, and plastic sheeting. I also put in air stones to increase the oxygen content of the water. I monitor the undercover temperature and the water temperature remotely. I live west of Chicago and after a few 0 degree days my pond is not frozen. The coldest the under cover temperature has been is 31.4 degrees and 37.9 degrees for the water. If this works out I plan to cover the pond again next year but make it high enough to stand under.
What reassuring information! I have a 1500 gallon pond that is 3 seasons old. I am used to my koi wintering over during the winter months. But I’ve never experienced ice! I live in Atlanta and we are experiencing an ice storm right now. Power outages are inevitable. I’m worried that if our power goes out, my pump, aerators, filters, etc will stop as well. Right now, the pond has not frozen over because the water is flowing down the waterfall. I assume it will freeze if the power goes out. Instead of worrying, I will do as you say and enjoy the beauty of it knowing full well that my koi are okay. Thanks so much for your blog! VA
Hey Virginia, I’m glad this was of help. Good luck with that nasty weather coming your way! Mike
I have a pond that holds about 1400 gallons. I have fish in there at the moment. Have tried over the years, and they seldom all make it through the winter. I use a pond heater to keep a hole in the ice. I was thinking about adding a second one on the other side of the pond. But I was also wonder about circulating the water as well, but I am not sure what size air pump to buy. And would i need to put the hose in the middle of the pond? I was looking at a Pondmaster air pump. I bought eight Koi earlier this year and would really like to see them come spring. When my pond freezes, it typically freezes until spring. Last year lost them all even with a hole in the ice.
Thoughts and advice?
Hello Stephanie, thanks for commenting! Yes you should have an air pump going during the winter months and the PondMaster air pumps are pretty good choice. Make sure you choose a model that will be strong enough to push to the bottom of your pond and try to use (2) points of aeration! -Mike
I have a small backyard pond – about 12 feet long x 5 feet wide by 2 1/2 feet deep. I added 5 small goldfish about 2 months ago. I wasn’t thinking ahead and did not buy a deicer. The pond is frozen and I’m not sure if the fish will live through the night if there isn’t an area of the pond that isn’t frozen. It’s too late tonight to go to a store – they are all closed. It is 12 degrees and will be all night long. What do I do if I can’t get to a store until tomorrow?
Hello Tina, I hope this reply is not too late. I’m going to say that it is pretty likely your fish will do ok in the short term. Unfortunately I don’t think there would be much that I could recommend doing with 12 degree weather. Once the stores are open I not only recommend a de-icer but also using an aerator during the winter months as well. I hope your fish are ok! Thanks for reading the blog and if I can help any further I am happy too. -Mike
I have a 1/4 acre pond with trout in it that is 9-10 ft deep at the deepest point. I have an 1/4 HP aerator in it running 24/7 and the water did not seem to be freezing over at all around it until we got a couple really colds days of weather and the whole pond froze over. The aerator is at the deepest part of the pond and I really don’t want to move it around every fall to shallow water if I don’t have to. The pump is shared between 2 – 1/4 acre pounds and the other pond has plenty of unfrozen water but the air hose length is about 1/4 the length into that pound as the one that froze over. I think I am hearing really nothing to worry about as long as the aerator is running right?
Yes, as long as both diffusers in each pond have air bubbles coming up you should be ok. When one length of hose is shorter than the other length of hose the shorter hose will usually get more of the pressurized air; so be sure that the diffuser that has the longer length is still blowing bubbles!! Ideally you should be moving the diffusers to a shallower area of the pond during winter, but many people do not move them, it is not always a problem, however the “best practice” would be to move it to a shallower zone, OR keep your diffusers in an area that is not too deep and not to shallow so you don’t have to move them each season..
OK I can’t really move the diffusers now but I adjusted the flow so there is more bubbles in the small pond (were the fish are at) and less in the swimming pond (that never froze over) in hopes the small pond will not freeze over again. If the big pond freezes over now not to worried about that because there’s no fish in it but I still want to reap the aeration benefits in it so that the muck continues to be cleaned up by bacteria there.
Hi. Thank u so much for this informative blog!! I live in New York on Long Island. This past winter has been exceptionally cold. Even with a bubbler, my pond froze over a few times. My pond is about 5000 gallons. The depth is 24 inches in the center. I hired people who claimed to be experts to re- do my pond!! The last expert robbed me of $13000.00 dollars. I feel like a fool. I’ve been hoodwinked on more than one occasion in hopes that my pond could work efficiently so that I could enjoy my beautiful fish. In the ice I observed one of my koi frozen!! You could just imagine my horror!! And that was in December. Since then, the pond has been at a constant freeze. I am panicked and I pray my little guys are alive. My point here, is that, I have learned a very expensive lesson. Please be careful not to hire landscapers or concrete contractors claiming they know how to build ponds. Please do the research needed!! And if anyone knows of any good pond builders on Long Island. Please email me at firstname.lastname@example.org. Thank you
I made the mistake of trying to break the ice during a couple of really cold days.
Now my pond is dropping water level 3-4″ in 24 hrs. Pond size is 6×10 ft, 32″. Has this resulted in damaging or cracking the liner.
Thanks for response.
Hello Mike, thanks for reaching out. It is difficult for me to say whether the liner has been compromised, but I would guess that it was not affected by opening the ice.
Is it possible to winter fish in. A 55gallon preformed pond? Such as the one in the website I posted from Amazon? I live in Calgary and we have somewhat cold winters but usually get plenty of Chinook winds which warm things up to around +5 celecious. This is my first pond.
Hi Paul, thanks for reaching out. I do think it would be a bit of a challenge keeping fish outdoors in a 55 gallon container during colder temps, and the possibility of cold snaps could be deadly in such a small volume of water. I’m not sure I’d take the risk and would maybe try to keep my fish indoors for the winter. Good luck! -Mike
i have three filters running in my pond, so three sources of running water. is this enough so that i do not need to keep a hole open. which i have done with boiling water. tired of that
Hi Elizabeth. On the face of your question I’d say it sounds like you should not have to use boiling water; however, there are too many variables and unknown info about your pond that I am not aware of to give any solid advice on this… 🙁 Tell me more! -Mike
The new home we just moved into came with a small decorative koi pond. It’s about 4 feet long but I’m not exactly sure how deep it is. It came with many very small koi fish all around an inch or two long (or less). The pond appears to have recently frozen over. Is this a problem? Will the small koi be able to manage? We currently have -6 C weather. Thanks in advance.
Hello Amanda, congratulations on your new home and new pond! Generally speaking your fish should be ok still, but I am missing alot of information. I would recommend using some sort of aeration for your pond during the winter months. You will not have to feed your fish until Spring and water temps are higher. -Mike
Hi Mike. My concern for my pond is during the summer month the water level reduce due to lack of rain. With the change in the temperature for this winter, the water was warm at various time than would freeze. I notice this was first year I seen so many fish surface in this winter. Our reason change in temperature that cause the pond to freeze, I am now find fish frozen at the surface. The aeration system has been on , an you tell what cause this and what can I do now to prevent even more deaths. Thank you
Hello Muriel. Thanks for reaching out. I’m very sorry to hear about your fish. Unfortunately I don’t have enough information to really be able to tell you what may have happened since there are numerous variables that could have affected your livestock. I usually recommend that my customers move their aeration diffusers to shallower water in their pond during colder season. Sorry I cannot help that much… -Mike
Hi, I have a seven foot by five foot pond with about fourteen goldfish, I put in a small round pond de icer but it is not working this winter pond totally frozen over. Should I get a stock tank de icer and would that be very expensive electricity wise or wjhat to do now. Thanks. Pond is about three and a half footdeep.
Hello Ruth. That frozen time of year huh! You can certainly use stock tank de-icer and they will work very well. If electric cost of running is a concern then just look at other “pond de-icers” and maybe not the stock tank types which tend to be more powerful and a bit more to run. Pond de-icers will give you a choice of different power levels and for a 7X5 pond a 600 watt de-icer may just do the trick instead of a 1200+watt stock tank type. Good luck, keep warm! -Mike
What would you recommend as the newest state of the art deicer for the backyard pond that is 16×18 feet in size 24 inches deep. I would like to keep a larger area defrosted other than the usual little circle. is there something that would keep the water temperature warmer. I live in Colorado.
Hey Rick. Thanks for reaching out. The technology in de-icers has not changed much in the last 10 years or so. I’d recommend using a good 1200 watt floating deicer, in combination with a good outdoor air pump for ponds. With those 2 pieces of equipment you will not likely encounter any issues with the pond even with complete ice cover. Neither of these will keep the water any warmer, but will allow the pond processes of de-gassing and oxygenating to happen very efficiently. To actually warm the body of water a pond heating $y$tem would need to be used, and installed ($$$$) when there is no ice on the pond.
Hi Mike, We live Ashvill, NC and have a 4 1/2 ft deep pond which finally stopped flowing this morning. We have an upper pool with no fish which flows down three levels to the larger pond with eleven small goldfish and two medium koi. It got down to 12 last night and is now 19. Is it advisable to melt a hole in the ice or pour hot water into the upper pool? Should we turn off the pump for the rest of the deep freeze? The pond has been kept clean of debris but has two underwater plants. I’d hate to loose those two koi.
Hello Angie. Some crazy weather huh?! If you pond stopped flowing then it would be good to disconnect the pump at this point. I’d not do the hot water thing, but would look at putting in a de-icer and/or aerator until things thaw a bit. If you need some local professional help you can reach out to Mike Wheeley at American Aquascapes. phone 336.578.6123
Thanks for your article. However, I’m a little confused and am asking for clarification. Your article appears to say having the pond frozen over is not problematic. But then in some of the comments sections you describe the need for a hole, aerator, deicer. I have a 3000 lb. koi pond that has a depth at it’s center of 3 1/2 feet (elliptical shape with about a 10 foot circumference at its widest point. Besides some algae, a few stray leaves, and the roots of some water lilies, it was reasonably clean before winter. I turn off all pumps and filters in the winter. I run a small aerator which typically keeps a hole in the ice. This consistently cold weather has frozen my pond over despite this. I have a small deicer which I placed on the frozen ice, but it is too thick to do any good at this point. I tried the boiling water method, but again the ice is too thick. It did make the ice soft enough where I could (in a reasonably quiet and gentle way) get an ice pick in and determine the ice to be about 4-5 inches thick, so not\ fear of freezing through (plus with the depth of 3 1/2 feet in center where the fish go in the winter I feel OK about that). I am worried about gas release, especially since I did have some plant roots and algae in the pond. Was considering finding an ice fisherman to quietly make a hole with a hand auger. Or should I leave it alone? It’s been about two weeks now. It’s supposed to get a little bit warner this week – up to 30 – whoo hoo! Thank you in advance for sharing your expertise.
Hi Marsha. Thanks for reaching out and checking out the blog. It is true that having the pond frozen over is not a problem generally speaking, however; for it to not be a problem certain conditions should be met as described in the article and which sounds like you have also met. Those “conditions” in a nut shell are to not go into winter with a dirty nutrient loaded pond, but there are many variables to consider that the article cannot truly cover. For example a pond keeper may have a really clean pond going into winter but they are crazy overstocked with fish and that could create issues or their aerator is way too powerful for the size pond they have, so again there are too many variables to get into specifics in a blog post so please take my information in a general sense of what I am presenting. I am always available to talk about a specific pond if any pond keeper would like to contact me and talk about their specific circumstances, the advice can be more pin point. To make my statements clearer still; a pond that has a complete ice cap is not a problem (generally) but it is highly desirable to have an area that stays open to allow for MORE EFFICIENT gas exchange to take place. If that hole does not exist it does not mean that the gas exchange isn’t taking place, but it is not taking place as efficiently as when the open area of water is present. A de-icer with help facilitate that and an aerator will really help quite a bit with the efficiency of allowing gas to escape and oxygen back in. I hope this helps clarify a bit more! If you need anything else please do contact me again. My email is email@example.com and my phone is 908.277.6000 Keep warm and I too can’t wait for some balmy 30F weather whooo hooo!!!! 😉 -Mike
Eastern PA here, temps have been single digits for but and pond froze over. Obviously there was a fish kill because I didn’t put in the equipment or fix the outlet needed there. However, my question is actually what would be the cause of JUST the koi (various sizes) dying off while the commets and gold fish are happy as ever swimming back and forth? I would have figured this might be backward. Pond is 1000gal just shy of 3ft deep, and was clear before the cold snap. And yes we use salt as per the recommendation of our pond store.
Hi Jeff. Very sorry to hear about the fish kill. That’s heartbreaking thing to deal with. I’ve seen the scenario you described with koi dying yet the goldfish doing just fine, not just in cold but also very hot weather. I believe it is likely due to oxygen deprivation. The larger koi fish require significantly more oxygen than the smaller goldfish, and the goldfish also will have easier access to taking atmospheric oxygen from the top of the pond if need be. However, there are many variables to be considered and the die off could have been caused by any number of things and there is too much information that I do not have, so I can only give a general idea of that happened. I’d probably see if the local pond pro might be able to check out things for you in the case that there is a greater issue going on. Again sorry to hear about that fish loss.. -Mike
We purchased a home in July that came with a small decorative koi pond. We had been doing well at managing the pond, but then this hard freeze came thru. We had left the waterfall running until it finally froze solid and cut off. This morning after some warmer temps the pond has thawed enough to see into the water again. To my dismay I can see one of our fish on it’s side. Will dormant fish lay over or has this fish not survived. I will definitely look into some of your previous suggestions of areators and such.
Hello Megan. A fish lying in it’s side is not necessarily dead, although it could be. Try to take a close look to see if its gills are at least moving very slowly. It is a pretty common behavior that can be caused by a few different factors from wild swings in barometric pressure which many of us are dealing with, as well as just general stress from low temperatures. Parasites are also a possibility. If you have a local pond pro that can take a look I’d suggest that since you are still fairly new to pond/fish keeping. BUT don’t poke it or try to get it to swim around either (which many people tend to do), that will likely further stress the fish out. Thanks for reaching out, and best of luck!! -Mike
Well – it seems like I already made a few mistakes. I have a small formed pond about 6′ x 3.5′ x 18″ deep. I had a small stock pond heater going, and it just recently stopped working. I also had a pump with a frog spitter that also quit around the same time – very aggravating they both quit at the same time. The pond is surrounded by deep snow that I cannot get to. I was able to break the 1″ ice layer with a long stick – which I now see I shouldn’t have done! I had several medium goldfish that I saw swimming around during a very warm spell the last 2 weeks of February.. We had a prolonged cold snap with a lot of snow since the beginning of March, and I haven’t seen anything of them since the warm spell. I also had a wood frog that adopted the pond as his own since the summer, and I saw it dive into the pond bottom during that warm spell as I approached it. I later read that wood frogs can survive almost being frozen to death. I am worried- should I just let all be until the weather warms, or try to put in another heater? This is my first pond, and set it up as a frog haven. Any ideas?
Hi, very similar to Megan’s entry on January 13, we inherited a small koi pond on purchase, had three koi until September. Koi count dropped to 2 and then to 1 even though I could not see any dead fish. I then saw a Heron standing on the side of the pond so immediately bought a heron net. Remaining koi lasted through first freeze-over which lasted a couple of weeks. The subsequent freeze two weeks ago has now gone but sadly he did not survive this one. I had a waterfall running the whole time to try to keep the water moving very slightly and have some aquatic plants in the pond. Could I have done anything else or is there something about a koi being on its own for such a long, cold, bleak period that I may have had no control over?
Hello John. It sounds like a combination of several factors were at work with probably no one factor any more responsible than the other. I am sorry to hear about the loss, but get back on that bike!! Good luck! -Mike
I have a natural earth bottom pond, it’s approx 50 ft by 50 ft and about 7 feet deep in the center. I just took 5 koi that had to be moved unexpectedly. They are about 7 inches long. They are the only fish in the pond. During warm weather we have a larger water fall going, but remove the pump in the winter. Now that there are fish, am I going to need to worry about keeping the ice open? If so do you have specific equipment recommendations for a pond this size. Are native fish less sensitive to gas buildup? I live in Michigan.
Hello Penny. Thanks for reaching out. I would suggest using aeration for the pond since you have stocked it. There are many options for aeration depending on your budget. I would probably use a strong single diffuser aerator and place the diffuser at about the 3′ depth. I don’t think native fish are any less sensitive to gas buildup, but koi would be MORE sensitive to gas build up. Good luck! -Mike
I live in Michigan, and my pond, (5x7x2), will freeze this winter. I have an aerator to keep a spot open, and the pump/filter discharges into a smaller, upper pond, which flows into the lower, larger pond where the fish are.
I also use a smaller pump/filter in the larger pond and the discharge is directly into this pond at the bottom, which creates a current around the pond, which the fish love. Is it a good idea to keep this current going all winter?