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 minimize the damage.
At a Glance: Protecting Your Pond from Extreme Cold
- Drain your plumbing if you shut down your pond.
- Use an aerator to prevent fish suffocation.
- Use a deicer 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 usually OK. A running waterfall can 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.
Why? That 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.
If you decide to keep your pond running in the extreme cold, you'll need to keep an especially close eye on it. Make sure your pump is running as usual - that means not stalling or making weird noises - and address ice issues as quickly as possible.
2. 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 disturb the water's surface and help prevent your pond from freezing over.
3. Deice - 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'll need a little extra help from a deicer.
Deicers float in your pond and keep a hole open in the ice, letting the gases that your fish exhale escape out of the pond.
A deicer 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 deicer 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 deicer, we don't recommend running a deicer without an aerator.
Another nice feature with deicers: They're thermostatically controlled, shutting off when the water warms up. That means you never have to worry about your deicer wasting electricity.
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 deicer 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. Of course, no method is foolproof. An especially cold few days could take out a few fish in even the best-prepared pond.
But 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.