• Archives

  • Categories

  • Pages

  • Follow me on Twitter

I heard you can lose fish during the winter. How do I prevent a winter fish kill? | Ponds & Lakes Q&A

Q: I heard you can lose fish during the winter. How do I prevent a winter fish kill?

Q: I heard you can lose fish during the winter. How do I prevent a winter fish kill?

Jon – Little Suamico, WI

A: Imagine being cooped up all winter long in a room with no ventilation and no fresh air. Pretty claustrophobic, right? Now add the stench of decaying garbage and other waste buildup … it’s likely you wouldn’t last until spring.

It’s a similar situation with your fish.

In colder climates that freeze over the winter, decomposing vegetation and waste beneath the ice layer releases toxic gases that build up, displacing the oxygen that the fish need to survive. When that O2 is replaced with ammonia and other harmful gases, the result can be a winter fish kill.

So how to do you prevent this from happening? Aeration with an Airmax® Aeration System.

Open a Window!

An Airmax® Aeration System sized for your lake or pond moves the water below the frozen surface, which keeps an air hole open in the ice. This ventilation allows the harmful gases to escape while bringing in fresh oxygen for your fish. The aeration also injects oxygen into the water via the bubbles that come out of the diffuser or air stones.

Provide Year-Round Oxygen

For the health of your fish, we recommend you run an aeration system year-round—unless you plan to use the pond for winter activities, like ice skating or hockey, that require a solid and safe sheet of ice. In that case, follow the instructions in your product manual to safely turn off your system.

Create a Warm Zone

If you plan to run your system year-round, move the diffuser plates into shallower water during the winter months. This will allow your fish to hunker down in your pond’s warmer depth for the winter. It will also prevent the rare “super cooling” effect, in which the water temperature dips below freezing and over chills your fish.

Pond Talk: Have you ever experienced a winter fish kill? What changes did you make to prevent it from happening again?

Aerate Your Pond in All Seasons - Airmax® Aeration Systems


Enjoy this article?
Join over 60,000 fellow pond owners and receive our Weekly Pond Talk every Saturday.


9 Responses

  1. We have a Pond air 2 pump and ran it last winter. Fortunately, we also ran a pond breather because condensation somewhere in the air lines froze when the air Temps got below zero and blocked off the air flow. I had to unplug the pump to prevent damage to it. In the spring I checked the reflux valves and they were fine. Is there a heated airline available for this system?

    • Hi Ann – Unfortunately we do not have any heated airline. If this happens again you may want to try and use a hot bucket of water to help melt the ice where the airline enters the pond. Chances are the entry point is where the ice would have formed. Not sure this is the case in your situation but many times a pond might freeze over on cold nights even with aeration but the air may still be pumping in under the ice. The more agitation at the surface the harder it is for ice to form so keeping airstones in shallower water may also help keep the ice open.

  2. a few winters ago i lost all my fish (bass and minnows) and commented on the Pond Blog about it — consensus was that a heron might have gotten them. In a winter fish kill when your fish die, can I assume they would float to the top? They wouldn’t just disappear, would they? There would be ample but sad proof of what happened

    • Hi Silva – Sorry to hear of your fish loss. In many cases of fish kill from a spring turnover you do see many float but I’ve seen fish both float and sink so it really depends on the circumstances of the kill, how long they have been gone before being discovered, etc.

  3. Can you add info about fish and pond care for us in the south? I’m in Houston and we get a few freezes but never ice over. My goldfish seem to be hungry all year! I do have one of your tents to keep out all the leaves.

    • Hi Mary Ann – If you only receive a few short periods of cold weather and never really have ice cover over the pond then you are probably ok to just keep your pond running. You can continue to feed Spring & Fall wheatgerm based foods as long as water temperatures stay above 40 degrees. Here are some articles geared more towards care for koi and goldfish. Dormancy, Cold weather feeding and switching fish foods.

  4. We have a 5/8 ac pond with plenty of bass and gill….well up til now!
    We’ve had 2-3-lb bass , but since mid summer I haven’t caught or seen any.
    No one else fishes the pond except the wife and I. Is it possible they have passed on to “fish heaven” ? If they died would they float to the surface? We have no large turtles, only little ones and just a few.
    It has been dry here this summer, but the water level is maintained with a well. I do catch a few 1lb er’s but no big ones since last spring..
    Pls. help
    Ralph Clark, Slanesville, wv

    • Hi Ralph – I can think of a couple possibilities. Have you seen evidence of any other predatory animals such as herons, raccoons..etc? Do you still have an ample supply of bluegill or have they disappeared as well? If you are catching small bass and see no bluegill it may be possible that the population is unbalanced and additional prey fish may need to be added. We recommend having triple the prey fish over the predatory fish like bass in order to maintain balance. If the fish just went to “fish heaven” it is tough to say without any evidence. Usually if there is a quick large fish kill you will see evidence but depending on how long its been and the circumstances that caused it, they may not always float to the surface.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: