You probably know your fish can survive a normal winter. But what about near-zero, negative-windchill temperatures?
Bitter cold has slammed parts of the U.S. over the past couple winters, with some areas seeing days of single-digit-and-lower temperatures. And if you think you feel cold huddled inside under an electric blanket, just imagine how your fish feel.
Extreme cold can wreak havoc on your pond life, not to mention your pump and other plumbing. You can, however, take steps to prevent damage and keep fish happy and healthy.
(By the way – these instructions are specific to ponds. If you have a disappearing pondless waterfall, click here).
At a Glance: How to Protect a Pond from Extreme Cold
- Drain your plumbing if you shut down your pond.
- Top off the pond periodically if you keep it running, and watch for obstructions caused by ice.
- Use an aerator to prevent fish suffocation.
- Use a de-icer to keep a hole open in the ice.
1. Shut Down Your Pond and Drain Your Plumbing
Some people prefer to keep their ponds running all winter long – and that’s OK if you’re willing to keep a close eye on things. A running waterfall can help circulate desperately needed oxygen to the fish huddled deep under the water’s surface, as well as keep a hole open in pond ice.
Extreme cold, however, presents a new set of challenges. Your pond could freeze over entirely, sending flowing water over top of the ice and out of your pond. Your pump could struggle to do its job in the frigid temperatures. Shutting down your pond can prevent these problems.
Drain your pond’s plumbing if you decide to pull the plug for the season. If you have a pump connected to a check valve, that means disconnecting the check valve assembly after you turn everything off. (Check out our video above to see how it’s done.)
The check valve prevents water from moving backward into your pump. If you turn off the pump without removing the check valve, that water remains stuck in the pipe, where it can freeze, expand and do devastating damage to your plumbing. We recommend bringing the check valve assembly inside for the winter after you disconnect it to prevent any weather-related damage.
The pump can stay outside in the bottom of the skimmer, where you’ll want to let it run for a few minutes about twice a month in the winter to keep everything loose for spring.
Most pond owners make the decision of whether to winterize their pond in November or December. If you find yourself questioning whether to keep things running come February, though, you can do a shutdown mid-season. Just make sure to follow all the steps above. (If you find that your check valve assembly is frozen when you go to remove it, you may need to use hot water or a heat gun to thaw it out. Pond Clean-Out Gloves also help make the job a little more bearable.)
2. If You Keep the Pond Running, Watch Your Water Level
If you choose to keep your pond running, you need to add water throughout the winter to compensate for the water that turns into ice. You’ll also need to keep an eye out for icy obstructions in the waterfalls or elsewhere that could cause water to flow out of the pond.
3. Aerate, Aerate, Aerate
Lack of aeration is one of the most common causes of winter fish deaths. Don’t let your koi become another statistic.
Most pond fish enter a semi-dormant state called torpor in the winter. Their metabolism slows, they stop eating and they find a nice, warm pocket of water deep in the pond where they can wait out the cold.
Fish in torpor, however, still need to breathe – and an iced-over pond can prevent them from doing that.
We recommend adding an aerator to your pond to ensure adequate oxygen circulation, especially if you have your waterfall turned off for the season. An aerator will not only bring in much-needed air, but it will also break the surface tension of the water – letting bad gases escape the pond.
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4. De-ice – But Be Nice
An aerator might do enough on its own to keep your fish breathing easy during mild winter weather. When the mercury really drops, though, you might need a little extra help from a de-icer.
De-icers float in your pond and keep a hole open in the ice. When you place your aeration diffuser below the de-icer, these two tools work together to let bad gases escape the pond.
A de-icer will heat up just enough to do its job; it will not cause a significant increase in your pond’s overall temperature. That means your fish will still enter torpor as the temperatures drop, and parts of your pond that aren’t close to the de-icer will still freeze over – which is OK!
Remember: always run an aerator in addition to a deicer. While you can sometimes run an aerator without a de-icer, we don’t recommend running a de-icer without an aerator.
Another nice feature with de-icers: They’re thermostatically controlled, shutting off when the water warms up. That means you never have to worry about your de-icer wasting electricity.
Find a Deicer at our Online Store
What if your pond freezes over despite your best efforts? You’ll need to find some way to make a hole yourself.
You have a few options:
- Place a pot of hot water on the ice and watch it slowly melt through. You may need to do this a couple times depending on the thickness of the ice.
- Use a rough-toothed saw to cut a hole.
- Buy a de-icer if you don’t have one. Our 300 Watt deicers typically melt through about 1 inch of ice per hour. (Your ice might end up 2 to 6 inches thick in extreme cold.)
Regardless of what method you choose, the key here is to avoid smacking your ice. Your fish – already in a delicate state because of the weather – might not be able to handle the ruckus caused by a two-by-four repeatedly thwacking the ice above them.
The vibrations from this kind of blunt force could even hurt or kill your finned friends. Fish have a series of organs that make up a mechanism called the lateral line, which they use to sense movement, vibration, depth, water pressure and orientation. The shockwaves from a garden gnome, shovel or other blunt object repeatedly smacking the pond can damage this line and cause serious damage to your fish.
Following the steps above will usually help your pond life and plumbing survive even the coldest Pennsylvania or Maryland winter.
If you make sure you drain your plumbing and provide plenty of air for your fish, your pond has a very good chance of making it to those beautiful spring days unscathed.
How Can I Make a Hole in My Pond’s Ice?
What Do Fish Do in Cold Weather?
When Should I Switch to Cold Water Food?
4 Tips for Fall and Winter Pond Care
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