How to Winterize a Pond

a pond with lily pads in winter, surrounded by frosty grass

We love the tranquility that an outdoor pond brings to our lives. The stillness of the water, the knowledge that your humble little oasis teems with aquatic life underneath, the satisfaction you get when you spy some of the more elusive critters making use of it--just gives us goosebumps of the good kind!

When you live in colder climes of the country, you have to take some extra steps to make sure your pond and its denizens survive the winter. You made the effort to install it. Here's how to keep it safe when temps plummet.

Clean the Pond

If you haven't done any fall clean-up yet, time to get out there before the weather traps you inside. Get those yard leaves raked so they don't blow into the pond. And before you drop them into the green bin, consider setting them aside to create some leaf mold to add micro-nutrients and improve soil structure in your garden.

This will take away most of the leaves and debris that would otherwise add to the muck you need to clean out. All that wonderful organic material is deadly when allowed to decompose at the bottom of your pond. A thorough clean-up is essential to remove the matter that could lead to a toxic buildup of gases, potentially killing anything overwintering in the watery depths.

man in boots cleaning out a large pond in fall

Prune the Plants

After cleaning out the detritus, trim the foliage of any pond plants. These guys will go dormant during the winter so remove leaves and prune stems down to the base and add them to your compost pile. Like those fallen leaves, this decaying organic material can create toxic living conditions that can be detrimental to your fish friends below.

Once the plants are all trimmed up, determine whether they'll be stored inside or outside. Cold-hardy plants like hardy water lilies can simply be reinstalled back into the pond after being pruned. Place them in the deepest part of the pond so they remain completely submerged. Tender plants like tropical water lilies or water hyacinths may need to overwinter in a protected space like a garage, basement, or greenhouse.

hand lifting goopy plant growth out of pond

Add Cold Water Bacteria

Cold water bacteria are a beneficial strain of bacteria that continue to do their jobs even when the temps fall below 50 degrees. Adding it to the water will improve water clarity and quality, helping to keep your sleeping fishies nice and healthy. The bacteria works all winter long to break down fish waste and reduce ammonia and nitrites, thereby reducing the buildup of toxic gases during those cold winter months.

Turn Off the Pump

While this isn't necessary (see following option) if you opt to remove the pump for storage indoors, you're also extending its life. Clean the filter and drain any water out of the plumbing and store them indoors. Place a small re-circulating pump near the surface of the water to help oxygenate it and to provide movement so a small hole remains open on the surface in the event of a hard freeze.

Alternative: Leave the Water Running

You may not be able to remove the pump before Mother Nature decides to bring down the temps. Hopefully, you at least got around to cleaning the pond since removing the pump isn't an essential task. You can keep the pump running as long as you check on it periodically as the season progresses, meaning you'll have to put down your hot chocolate and don your snow boots and parka.

Check the water level, topping it up as it evaporates. After topping it up, check that those beautiful ice formations that you've been admiring from your cozy kitchen haven't formed a dam that diverts the stream from its regular route. Wasted water is a no-no.

Whether you decide to remove the pump or keep the water running is a matter of preference for the pond owner. Whichever option you choose, you'll have to follow a distinct set of maintenance rules to keep things humming along.

large fish in an outdoor pond

Take Care of Your Fish

The best way to ensure your fish make it through the winter is to send them into those cold months in tip-top health. Once the weather cools down, so does the fish's metabolism. Their digestion slows so they don't need to eat as much. Reduce their feeding appropriately, otherwise, you're just wasting food and adding more organic matter that will end up polluting the water. When water temps dip below 50 degrees, you can stop feeding altogether as they are preparing for hibernation.

Creating a happy haven for your fish takes effort, but from that effort, you can reap great rewards all year long!