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1st of all, Is your pond a big landscape pond in your backyard? Or do you have a koi pond or decorative feature near the patio? Strategies differ slightly for each waterbody, and your pond will most likely use one (or a couple) of these strategies to soldier on through the winter.
Whether you need to shut down your pond pump in winter depends on your location and climate. In the northern U.S., where ponds freeze over, pumps should often be shut down (or moved) to prevent water from supercooling and harming fish and damaging your pond infrastructure.
Instead, many pond owners switch to:
A pond heater (or de-icer for larger ponds)
A small pond aerator (or a larger pond aerator for big/deep ponds)
These allow good gas exchange and oxygen (DO) recharge.
In the southern U.S., pumps can usually run all winter since water rarely freezes entirely. The key is monitoring temperature, water depth, and fish behavior. If your pond is at risk of freezing, shutting down the pump and using a winter-safe system is the safer choice. Cooler water holds more oxygen, so your fish do not need as much circulation as they do in the summer. Keep an eye out for changes in water quality; large swings in water temperature can breed issues for your aquatic denizens.
Every winter, pond owners face the same decision: leave the pump running or shut it down. The wrong choice can stress your fish, damage your equipment, or leave you with a pond full of algae by spring. The right choice depends on where you live and what your pond is exposed to during cold weather.
In northern states—Minnesota, Wisconsin, Michigan, New York, Indiana, and Ohio—winter means ice cover that can last for months. A running pump in these conditions can actually make things worse, or not….it really depends.
A wintertime pond cannot be summarily ignored until spring. Monitoring the changing conditions will help you gauge which strategy(ies) you need to employ throughout the long winter.
The problem:
Super Cooling: Circulating water mixes freezing (ultra cold) surface water into deeper zones, lowering temperatures where fish typically overwinter. This can be detrimental to fish in the extreme.
Super cooling can happen only when the weather gets extremely cold and/or you are circulating WAY TOO MUCH WATER for the conditions.
If you have a large waterfall in a small pond, pull your big pump and get a smaller, internal filter pump to run during winter.
This smaller pump will filter out solids, keep a small hole open in the ice without endangering your fish.
Moving water under ice can create uneven freeze patterns or ice dams. This mostly leads to unattractive ice blobs and thin spots that are treacherous to walk on… So, please do not walk on/near deicing operations. Protect wildlife by making sure critters have a way to climb out if they fall in.
The solution:
Shut down the main pump before your pond freezes.
Move it out of the skimmer and into the pond for the winter. OR…
Store it indoors after cleaning to protect the seals. Store in water to protect the seals if the manufacturer recommends it.
Use a floating de-icer (in small koi ponds) or Ice Eater (in large ponds) to keep a small area open for gas exchange.
Add a bottom-diffused aerator to maintain oxygen levels through winter.
Clear leaves and debris before shutdown to prevent oxygen loss from decomposition.
Explore our Ice Eaters and Pond Aerators to keep your pond safe while pumps are off.
In states like Texas, Florida, Georgia, or the Carolinas, winters are mild, and ponds rarely freeze solid. That changes the equation entirely.
The problem:
Without circulation, mild winter ponds can develop stagnant zones.
Warm spells can trigger algae growth even in January.
Pumps that sit idle for months risk seal failure or clogging when restarted.
The solution:
Keep your pump running year-round to maintain circulation and oxygen levels.
Clean filters and intake screens before winter.
Reduce fish feeding to smaller, colder-water portions, but don’t stop entirely.
Switch to a cold water feed for easier digestion
Inspect your pump weekly, especially after heavy rains or storms.
Pair circulation with aeration to add an extra layer of protection for fish.
If you’re unsure, think through these points before making a decision:
Climate: Does your region experience sustained freezing, or only mild dips in temperature?
Pond depth: Shallow ponds freeze more quickly and leave fish fewer safe zones.
Fish load: Heavily stocked ponds need stronger oxygen support.
Backup systems: Aerators and de-icers provide insurance if you choose to shut down the pump.
Problem: Fish are struggling mid-winter.
Cause: Supercooled water from pump circulation in freezing climates.
Fix: Shut down the pump, switch to aeration (or a pond heater) to maintain gas exchange.
Problem: Murky water and algae in late winter.
Cause: Mild climates allow algae growth if circulation stops.
Fix: Keep your pump running, add winter-safe treatments, and skim debris.
Studies have shown that aeration is the safest winter tool in freeze-prone areas because it maintains oxygen without the risks of supercooling. This reinforces what many pond professionals recommend: pumps are for summer, aerators and de-icers are for winter.
If you’re in the north, shut your pump down before ice sets in and switch to winter-safe tools like de-icers and aerators. If you’re in the south, keep your pump running but maintain it carefully to support fish and water quality.
Either way, your pond will head into spring healthier, and your equipment will last longer.
Yes (but mostly no)—in freezing climates, pumps circulate cold water into fish zones. This can stress or kill fish overwintering at the bottom. This is rare, but not unheard of. If you see a brutal cold snap coming (i.e.,- 20 degrees for a week), make preparations. Decrease your circulation and switch to a less aggressive mixing option. An ice-capped pond is protection for fish in times like these. When the weather clears, punch a hole in the ice and turn your pump back on. Your fish will survive a week or so under ice in most situations in small koi ponds; they’ll survive much longer under ice in larger systems.
If you shut it down, clean it, and store it indoors in a frost-free spot to protect seals and extend lifespan.
Sure, but have a backup plan. In northern states, use a floating de-icer or Ice Eater instead of relying on a pump.
A combination of a bottom-diffused aerator and a de-icer provides the best balance of oxygen and open water. For small ponds, use a small filter pump or a tank heater to keep a hole open.
In freezing conditions, waterfalls often freeze into ice dams, leading to overflow. In mild states, waterfalls can usually run year-round.
