How to Look After a Pond in Winter

Key Takeaways:

• Stop feeding fish entirely when water temperatures consistently drop below 4°C (39°F).
• Keep the main submerged pump running 24/7 to oxygenate beneficial bacteria, but turn off waterfalls and UV clarifiers.
• Never smash pond ice; use a pond heater to keep a vent hole open so toxic gases can escape.

Freezing weather can pose several challenges for pond enthusiasts, from damaged equipment to causing havoc to pond life. With this in mind, pond winter care is essential, especially in extremely cold conditions where ponds risk freezing over entirely.

After the autumn leaf cleanup, pond owners must shift their focus towards safeguarding their livestock, pumps, and filters from the harsh winter conditions. Failing to do so can be fatal for fish and pond life, so it's crucial to be prepared! 

While pond winter care may seem daunting for beginner fish keepers, there are a few easy ways to protect your pond in winter. Here, we've compiled a comprehensive guide with invaluable tips and expert advice to assist you.

Jump to: 

Winter Pond Care Action Plan

Should I Keep My Pond Pump Running in Winter?

When To Stop Feeding Fish in Winter

What to Do if My Pond Freezes Over and I Have Fish?

How to Keep a Pond Warm and Prevent it Freezing Over

Should I Cover My Pond in Winter?

What to Do With Pond Plants in Winter

Clean Your Pond Before Cold Weather

The Essential Winter Shutdown Checklist

Winter Pond Care Action Plan

Should I Keep My Pond Pump Running in Winter?

Bottom Line: Leave your main submerged pump and biological filter running to keep fish and beneficial bacteria alive, but shut down waterfalls, fountains, and UV clarifiers before the first hard freeze.

Contrary to some recommendations, you don't need to completely shut down your pond pump during the UK winter.

The Main Submerged Pump (LEAVE ON): Your biological filter houses beneficial bacteria that help improve your pond’s water quality, benefiting fish health during colder months. Shutting down your pond pump and filter for the winter would essentially halt this essential process, leading to the demise of these beneficial bacteria. Running your main pump also maintains water circulation and prevents the pond from completely freezing over. 

Waterfalls & Watercourses (TURN OFF): Shut down waterfall pumps during prolonged freezes; ice dams easily form on watercourses, diverting water outside the pond and slowly draining it, putting your fish in immediate danger.

UV Clarifiers (TURN OFF & DRAIN): Freezing water expands and will quickly shatter the delicate quartz sleeve or the plastic housing. As a preventative maintenance step, lubricate your pressure filter seals (O-rings) with a silicone lubricant before winter hits, as freezing temperatures cause rubber to stiffen, crack, and leak.

Expert Insight: "The biggest mistake UK pond owners make is turning everything off in November. By keeping the main pump running but elevating it one foot off the bottom, you preserve the warmer thermal layer at the base of the pond where fish hibernate, while keeping the filter alive." - 

For an in-depth look at managing your filtration during cold weather, read our full guide: Should I Keep My Pond Pump Running in Winter?

When To Stop Feeding Fish in Winter

Bottom Line: Stop feeding your pond fish entirely when water temperatures consistently drop below 4°C (39°F) to prevent undigested food from rotting inside their digestive tracts.

Pond fish can typically handle colder months. Because they are cold-blooded, cold water slows their metabolism to a near stop, so they stop processing food. If you continue feeding pond fish a high-protein summer diet in winter, it can cause constipation and internal decay. 

As temperatures drop toward 10°C (50°F), transition your koi and goldfish to easily digestible wheatgerm pellets. Once the water hits 4°C, stop feeding them completely until spring. This is typically from the end of October through the chilly months until around the end of March.

For exact temperature timelines and diet adjustments, see our detailed guide: When to Stop Feeding Pond Fish for Winter.

Product Recommendations

What to Do if My Pond Freezes Over and I Have Fish?

Bottom Line: Never strike or smash the ice or pour boiling water in. Fill a plastic bottle with hot water and lay it on top of the ice to slowly melt an area.

If you find your pond frozen over one winter morning, avoid breaking the ice, as this can cause unnecessary stress for your fish.

While some people recommend pouring hot water onto the ice to remove the frozen layer, this can cause stress or serious injury to your fish, so it should be avoided at all costs; instead, we would recommend filling a plastic bottle with hot water and laying this on top of the ice to slowly melt an area.

How to Keep a Pond Warm and Prevent it Freezing Over 

Bottom Line:  Use a pond heater to keep a vent hole open, and turn off exposed water features.

Shallow ponds (under 3 feet deep) and raised above-ground ponds are more likely to freeze over in winter. If your pond freezes over, it traps toxic gases from decaying organic matter, which can suffocate fish. Using a heater to keep a hole in the ice, turning off the waterfall and using a pond cover are some of the best tips for preventing your pond from freezing over.

For more strategies on insulation and preventing solid freezes, check out: How to Keep Your Pond Warm in Winter.

Product Suggestions

Should I Cover My Pond in Winter? 

Bottom Line: Yes, covering your pond in winter prevents leaf buildup that causes toxic winter sludge and protects sluggish fish from predators.

Winter’s dropping temperatures can slow your fish's metabolism, making them less active and more likely to seek shelter. This is especially true without aquatic plants, as fish have fewer places to hide and feel safe.

This enhanced vulnerability for fish during winter makes them much more vulnerable to predators like herons. With this in mind, installing protective pond deterrents is essential for winter pond care. If you’re looking for ways to protect your fish, we recommend installing pond netting or heron deterrents during the winter months.

A net will also catch autumn leaves before they sink to prevent sludge that spikes ammonia and hydrogen sulphide levels under the winter ice. Secure the net tightly - if it sags into the water, the trapped debris will still rot and ruin your water quality.

If you skipped netting in autumn and are already dealing with a foul-smelling mess, learn how to safely get rid of it here: The Pond Planet Guide to Pond Sludge and How to Remove It.

Product Suggestions

What to Do With Pond Plants in Winter

Bottom Line: Trim back all dead foliage from hardy plants and lower them into the deep end to prevent roots from freezing, while bringing non-hardy floating plants indoors.

Pond plants play a crucial role in maintaining water quality and providing shelter for fish. With this in mind, protecting them is essential in pond winter care.

To prepare your pond plants, remove dead foliage and floating debris towards the end of autumn. This will prevent oxygen depletion occurring from decaying leaves.

Most UK pond plants become dormant during winter. However, some pond plant varieties are evergreen, including reeds like Equisetum hyemale and Juncus. Other pond plants, including Primula beesiana, Caltha polypetala, and Sisyrinchium californicum, may retain their greenery, but their leaves may become damaged if temperatures remain below freezing for an extended period.

To protect your pond plants, keep them submerged in water at least 10 cm deep during winter. This will shield your plants from most winter conditions.

Handle your plants based on their hardiness:

• Hardy Plants (Lilies, Reeds): Prune dead stems back to the crown. Submerge them at least 10 cm deep to shield the root systems from surface ice.
• Evergreen Marginals (Equisetum hyemale): Leave them in place, but monitor for frost damage.
• Non-Hardy Plants (Water Hyacinths, Lettuce): Pull them out completely before the first frost. Overwinter them indoors in a tub of water with a grow light, or discard them and replace them in spring.

Clean Your Pond Before Cold Weather

Clean your pond before temperatures drop below 10°C. This helps keep your fish active and less likely to sustain an injury during cleaning. Use a net to remove fallen leaves before removing sludge and organic debris with treatments and a pond vacuum.

Remember, water treatments for your pond are not just for warm weather. Arguably, controlling water quality is even a more important part of your pond maintenance in winter than any other time of year. You can prevent debris buildup that collects during winter by applying a quality fall/winter bacteria blend to the pond once a month. This will help keep fish healthy and happy through the winter months.

Product Suggestions

The Essential Winter Shutdown Checklist

Execute this checklist before water temperatures drop below 10°C (50°F) to prevent burst pipes, burnt-out pumps, and winter fish kills.

Do not wait for the first freeze to winterise your pond. Follow these steps to secure your setup:

• Clean the Pond: Net out all surface leaves and vacuum the bottom to remove organic sludge.
• Install Netting: Pull a pond net taut over the surface and peg it down securely so it doesn't sag into the water.
• Shut Down Waterfalls: Turn off watercourse pumps to prevent ice dams and water loss.
• Drain UV Clarifiers: Turn off the UV unit, disconnect it, and drain all water to protect the quartz sleeve from shattering.
• Winterise Pipes: Blow out all exposed plumbing lines and cap them with cleanout plugs at each end to stop trapped water from freezing and bursting the pipes.
• Lubricate Seals: Apply a silicone-based lubricant to all pressure filter O-rings to prevent the cold from turning the rubber brittle.
• Deploy De-Icers: Place your heater in the pond and test it before the ice forms.
• Switch Fish Food: Swap out high-protein food for wheat germ, and prepare to stop feeding entirely at 4°C.

Shop for everything you need to look after your pond in winter

By taking proactive steps before water temperatures drop - clearing organic sludge, transitioning your fish's diet, and protecting delicate filtration equipment - you create a safe, stable environment for your aquatic life to wait out the cold. 

Do not wait for the ice to set in before gathering your essentials. From heavy-duty nets to easily digestible wheatgerm, having the right tools on hand is the most effective way to prevent burst pipes, burnt-out pumps, and winter fish loss.

Shop for everything you need to look after your pond in winter at Pond Planet.