Winterization

Our pond winterization supplies cover everything you need to get a backyard pond or koi pond through freezing weather without losing fish or filtration. This category brings together de-icers, cold-weather aeration kits and air pumps, cold-water beneficial bacteria, and cold weather fish food, the core equipment most pond owners reach for once nighttime temperatures start dropping toward freezing.

Every pond handles winter a little differently depending on depth, fish load, and whether it freezes over completely or just skims ice on cold nights. A shallow patio pond with a few goldfish needs a different setup than a 5,000-gallon koi pond that ices over most of the winter. Below you'll find de-icers sized from small birdbath units up to full 300-watt pond models, aeration kits and air pumps built to keep water moving under ice, and the bacteria and food products that keep your pond's biology stable once water temperatures drop.

What Belongs in a Winterization Order

Winterizing a pond isn't one product, it's a short list of equipment that works together: a de-icer to keep an opening in the ice, an air pump or aeration kit to keep water circulating at depth, a cold-water bacteria product to keep the biology of the pond working, and a wheat-germ-based food to switch fish onto as the water cools. Not every pond needs all four. A pond that never fully ices over might only need aeration and cold-weather food, while a pond in a colder microclimate that regularly sees a hard freeze needs the de-icer running as well.

If you're new to pond ownership, start with a de-icer and cold-weather food, then add aeration once you see how your pond behaves in a typical cold snap.

De-Icers: Keeping an Opening in the Ice

A de-icer's job is simple: keep a hole open in the ice so gases can escape and oxygen can get in. It is not meant to heat the whole pond, and it won't keep water above freezing throughout. We carry de-icers across a range of sizes, from the K&H Ice Eliminator Birdbath De-Icer (50 Watt) for small water features up to the Aquascape Pond De-Icer (300 Watt) and the K&H Thermo-Pond Perfect Climate Deluxe Pond De-Icer for larger ponds that need more consistent output through a hard winter.

Choosing wattage and style

Wattage should roughly scale with pond size and how cold your winters typically get. A 50-watt unit is right for a small water feature or birdbath, not a full koi pond. Larger ponds, or ponds in spots that see extended stretches below freezing, do better with a 300-watt unit like the Aquascape Pond De-Icer (300 Watt) or the K&H Thermo-Pond Perfect Climate Deluxe Pond De-Icer, which runs on a thermostat so it only draws power when the surface actually needs it. The K&H Thermo-Pond 3.0 Floating Pond De-Icer is a mid-range floating option worth considering if you want something simple to place and remove each season.

Floating de-icers rise and fall with the water level, which is usually the easier setup for most backyard ponds. Plan on running the unit continuously once temperatures start dropping toward freezing rather than switching it on and off, since the goal is a stable opening, not intermittent thawing.

Aeration Through the Cold Months

Aeration and de-icing solve two different problems. A de-icer keeps a hole in the surface. An air pump or aeration kit keeps water actually moving, which helps gas exchange happen across a larger area and prevents dead, stagnant zones near the bottom where fish spend the winter. We carry the Atlantic Typhoon Air Pumps (TA1800-30LPM and TA3600-60LPM) as standalone pumps, along with the Aquascape Pro Air 20 Pond Aeration Kit and Aquascape Pro Air 60 Pond Aeration Kit, which bundle a pump with tubing and a diffuser.

Matching a kit to pond size

The number in each kit name (20, 60) roughly corresponds to the pond volume the kit is built to support, so a larger koi pond will need the Pro Air 60 rather than the Pro Air 20. If you already have a pump you're happy with, the Atlantic Typhoon Air Pumps are sold on their own and can be paired with diffusers and tubing you already have on hand.

Most pond owners run aeration alongside a de-icer through the coldest months, then scale back once temperatures climb back into the 40s. That combination, an open hole plus circulating air, is generally the most reliable way to keep a pond stable through a regular ice-cover winter.

Cold-Water Beneficial Bacteria

Standard beneficial bacteria products slow down or go dormant once water temperature drops into the 50s. Cold-water formulas like Microbe-Lift Autumn/ Winter Prep (AWP) and Aquascape Cold Water Beneficial Bacteria are formulated to keep working in colder water, breaking down waste and organic debris that would otherwise build up over winter and hit your pond as a spring cleanup problem.

Microbe-Lift Autumn/ Winter Prep (AWP) is designed specifically for the fall transition window, when water is cooling but hasn't dropped into full winter dormancy yet. Dosing before the water gets too cold gives the bacteria a chance to establish before their activity slows further.

Cold Weather Fish Food

Fish digestion slows as water cools, and standard high-protein food becomes harder for them to process. Wheat-germ-based foods like Microbe-Lift Legacy Cold Weather Fish Food (Wheat Germ) and Aquascape Premium Cold Weather Fish Food are formulated to be easier to digest in cold water, which matters because undigested food sitting in a fish's gut in cold conditions can cause more harm than not feeding at all.

These are transition foods, meant for the weeks when the water is cooling but fish are still active enough to eat. Once your pond drops into the range where fish stop coming to the surface, feeding typically stops for the season regardless of which food is in the bag.

Winter-Blooming Plants

Most pond plants go dormant for winter, but Aponogeton Distachyus 'Water Hawthorne' blooms in cooler water. It's a smaller addition, but worth knowing about if you want your pond to look like more than a bare de-icer hole in January.

Choosing the Right Combination for Your Pond

Pond size and fish load are the two biggest factors. A small water garden with a handful of goldfish can often get by with just a birdbath-style de-icer and a switch to cold weather food. A larger koi pond with a heavier fish load needs the de-icer, an aeration kit running through the winter, and a cold-water bacteria product to manage the waste those fish keep producing even in cold water.

Local climate matters too. In much of the Puget Sound area, ponds see intermittent freezes rather than months of solid ice, which means a mid-range de-icer paired with aeration usually covers it. If your pond sits in a colder pocket, gets more wind exposure, or is on the smaller and shallower side (shallow water loses heat faster), size up on wattage and keep the aeration running full time rather than only during hard freezes.

Budget is a factor too, and it's fine to phase this in. A de-icer is the single highest-impact purchase for pond survival in freezing weather; aeration, cold-water bacteria, and cold weather food matter less if your winters rarely dip below freezing.

When to Start Winterizing

Start watching water temperature in early fall. Once it consistently drops below 60 degrees, switch to cold weather food and consider dosing a cold-water bacteria product while the bacteria still has time to establish. De-icers and aeration kits should be set up and running before you get your first hard freeze, not after, since installing equipment in a pond that's already iced over is a lot harder than getting ahead of it.