As the days shorten and the water turns cold, your backyard pond needs a little help to make it through winter. Knowing how to winterize a pond protects your fish, your plants, and your equipment from freeze damage, low oxygen, and the buildup of toxic gases under the ice. The good news is that the process is straightforward once you understand the few steps that really matter. This guide walks you through cleaning out debris, dealing with tender and hardy plants, adjusting fish feeding, deciding what to do with your pump and filter, and keeping a vital hole open in the ice. Whether you live where the surface barely skins over or where ponds freeze solid for weeks, you’ll find a clear plan to follow.
Part of our Ponds & Water Gardens guide →
In this guide
- Why Winterizing Your Pond Matters
- Clean Out Debris and Net the Leaves
- Cut Back and Remove Tender Plants
- Stop Feeding Fish as the Water Cools
- What to Do With the Pump and Filter
- Keeping a Hole Open in the Ice
- Fish Care Over Winter
- Your Fall Winterizing Checklist
- Frequently Asked Questions
- Featured project by Gensou Aquascaping
Some links in this article are affiliate links. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you.
- Remove leaves and debris before winter so decay doesn’t foul the water under the ice.
- Cut back and overwinter tender plants like tropical lilies and lotus; hardy plants can stay in the deep zone.
- Stop feeding fish once the water drops below about 50°F, since their digestion slows dramatically.
- Whether you run or remove the pump and filter depends on your climate and whether the pond freezes solid.
- Always keep a hole open in the ice with a de-icer or aerator—never smash the ice, which stresses fish.
Why Winterizing Your Pond Matters
Winterizing isn’t just tidying up—it’s about protecting the living system you’ve built. When a pond freezes over completely with no opening, decaying organic matter releases gases like carbon dioxide and ammonia that have nowhere to escape. Trapped under a sealed lid of ice, those gases can reach levels that harm or kill fish. At the same time, oxygen can’t move into the water across a solid surface, so a sealed pond slowly suffocates its inhabitants.
Cold itself is rarely the main threat. Most hardy fish and plants are adapted to survive freezing temperatures as long as the deep water stays liquid and gas exchange continues. The real dangers are oxygen depletion, toxic gas buildup, and equipment damage from water freezing inside pumps, pipes, and filters. A little preparation in fall prevents expensive and heartbreaking surprises in spring.
Clean Out Debris and Net the Leaves
The single most important fall task is removing organic debris. Fallen leaves, dead plant stems, and uneaten food sink to the bottom and decompose over winter. Under the ice, that decay consumes oxygen and produces the very gases you want to avoid. The less debris you leave behind, the cleaner and safer your water will be.
- Stretch pond netting across the surface before the leaves really start to drop, then lift it off when full.
- Use a long-handled pond net or skimmer to scoop floating leaves daily during peak leaf fall.
- Trim back dead and dying foliage from marginal plants so it doesn’t collapse into the water.
- Remove sludge from the bottom with a pond vacuum or net if a thick layer has built up over the season.
You don’t need to scrub the pond spotless—a thin layer of beneficial bacteria and some leaf litter is natural. The goal is to remove the bulk of the material that would otherwise rot under ice.
Cut Back and Remove Tender Plants
How you treat your aquatic plants depends entirely on whether they are hardy or tender. Getting this wrong is one of the most common ways pond owners lose plants over winter.
Tender plants: tropical lilies and lotus
Tropical water lilies will not survive freezing and must be brought indoors. In cold regions, lift the tubers, clean them off, and store them in moist sand or peat in a cool, frost-free spot, or keep the plant growing in a tub in a heated indoor space. Lotus is trickier—some lotus are hardy if their tubers sit below the ice line, but in colder zones or shallow containers the tubers can freeze and rot, so many growers move potted lotus to a frost-free garage or basement and keep the soil barely moist.
Hardy plants
Hardy water lilies, hardy lotus, and most marginal plants can overwinter in place as long as their roots are below the level the ice reaches. Trim the foliage back, then lower the pots to the deepest part of the pond where the water stays liquid. Cut back marginal plants like rushes and irises, leaving a few inches of stem above the waterline.
Tropical floating plants such as water hyacinth and water lettuce are typically treated as annuals in cold climates—they die off with the first hard frost and are simply composted.
Stop Feeding Fish as the Water Cools
Fish are cold-blooded, so their metabolism is tied directly to water temperature. As the water cools, their digestion slows down. Once the water drops below roughly 50°F, koi and goldfish can no longer fully digest food, and uneaten or partially digested food can cause health problems and foul the water.
- As temperatures fall into the 50s °F, switch to a low-protein, wheat germ-based cool-water food.
- Feed less often and only what the fish eat quickly.
- Once the water is consistently below about 50°F, stop feeding entirely.
- Resume feeding in spring only after the water warms back above 50°F and stays there.
It feels counterintuitive to stop feeding, but a fish with food sitting undigested in a cold gut is at far greater risk than a fish living off its reserves in a state of near-dormancy. Use a simple floating pond thermometer to track the temperature so you know exactly when to taper off.
What to Do With the Pump and Filter
This is where climate makes the biggest difference, and there’s no single right answer. Your decision depends on how cold your winters get and whether your pond freezes solid.
Mild climates: keep running
Where the pond only freezes lightly or not at all, you can keep the pump and filter running through winter. Moving water resists freezing and keeps oxygen levels up. Just monitor for any ice that might build up around waterfalls and cause water to escape the pond.
Cold climates: remove or relocate
Where ponds freeze hard, many owners shut down the main pump and biological filter for winter. Running a waterfall in a hard freeze can pull warmer water from the depths to the surface and even create ice dams that drain the pond. If you shut the system down:
- Remove the pump, clean it, and store it submerged in a bucket of water indoors so the seals don’t dry out.
- Drain and clean the filter and any UV clarifier, which can crack if water freezes inside.
- Blow out or drain exposed plumbing so trapped water can’t freeze and split pipes.
If you want to learn more about choosing the right equipment, see our guides to the best pond pumps and best pond filters.
Keeping a Hole Open in the Ice
If you have fish, keeping at least one opening in the ice all winter is non-negotiable. That open hole is what lets toxic gases escape and oxygen enter. There are two reliable tools for the job, and they’re often used together.
- A floating pond de-icer is a thermostatically controlled heater that keeps a small area ice-free. It doesn’t warm the whole pond—it just maintains an opening.
- An aerator pushes air through a diffuser stone, and the rising bubbles plus surface agitation help keep a hole open while adding oxygen.
Whatever you do, never smash the ice with a hammer or hatchet. The shock waves travel through the water and can injure or kill dormant fish. If you ever need to open a frozen-over pond, set a pot of hot water on the surface and let it melt through gently.
Fish Care Over Winter
Once the water is cold and feeding has stopped, your fish enter a state of low activity, hovering near the bottom where the water is warmest and most stable. Your job is mostly to leave them alone and keep their environment safe.
- Make sure the pond has a deep zone—generally at least two feet, deeper in very cold regions—where water stays above freezing.
- Keep the de-icer or aerator running so gas exchange continues all winter.
- Avoid disturbing the fish; don’t poke at the ice or run noisy equipment near them.
- Place an aerator’s diffuser at a mid-depth rather than the very bottom, so it doesn’t pull up the warmest water and chill the deep zone.
If your pond is shallow or you live where it freezes solid for long stretches, the safest option may be to bring fish indoors into a holding tank for the season. A well-built pond with a deep area makes overwintering outdoors much easier—something worth planning for if you’re reading how to build a backyard pond.
Your Fall Winterizing Checklist
Pull it all together with this step-by-step checklist to work through as fall progresses:
- Net the pond surface to catch falling leaves before they sink.
- Remove existing debris and sludge from the bottom.
- Trim back hardy plants and lower their pots to the deep zone.
- Lift, clean, and store tropical lilies, lotus, and other tender plants indoors.
- Switch fish to a cool-water food, then stop feeding once the water dips below about 50°F.
- Decide whether to run or remove the pump and filter based on your climate.
- If removing equipment, clean it and store the pump submerged indoors; drain the filter and pipes.
- Install a floating de-icer and/or aerator to keep a hole open in the ice.
- Check that your deep zone is adequate, or move fish indoors if the pond is too shallow.
- Through winter, periodically confirm the opening stays clear and equipment is working.
For more seasonal guides and equipment reviews, browse our full water gardens & ponds collection.
Frequently Asked Questions
Can fish survive winter in a pond?
Yes. Hardy fish like koi and goldfish can survive winter outdoors as long as the pond has a deep zone that stays liquid, a hole is kept open in the ice for gas exchange, and you’ve stopped feeding them in cold water. In very shallow ponds or extreme climates, it’s safer to move fish to an indoor holding tank.
Should I drain my pond for winter?
No—don’t drain a pond that contains fish or hardy plants. They overwinter in the deep water. Draining is only appropriate for empty ornamental ponds or if you’re moving all livestock indoors and want to prevent freeze damage to the liner and equipment.
How do I keep my pond from freezing solid?
A pond with adequate depth rarely freezes all the way down. To maintain an opening at the surface, use a floating de-icer, an aerator, or both. These keep a small area ice-free so gases escape and oxygen enters, even when the rest of the surface freezes over.
When should I stop feeding my pond fish?
Stop feeding once the water temperature drops below roughly 50°F and stays there. Below that point, fish can’t properly digest food. Use a pond thermometer to track the temperature and taper off feeding as it cools, switching to a wheat germ-based cool-water food first.
Is it safe to break the ice on my pond?
No. Striking or smashing the ice sends shock waves through the water that can injure or kill dormant fish. If you need to open a frozen surface, melt a hole gently by setting a pot of hot water on the ice, and prevent the problem next time with a de-icer or aerator.