How to Winterize a Pond


It’s important to know how to winterize a pond of your own well before the winter months. Winter is coming or it’s already here.

Which means you need a quick and complete guide to figure out how to winterize that koi pond or water garden you built!

How to Winterize a Pond in 10 Steps

Here, we will be covering 10 simple concepts that will enable you to winterize your pond effectively.

When to Winterize Your Pond?

The following steps will most ideally begin in the fall right when you notice the leaves beginning to turn colors and the average temperature begins to drop.

Pond Fish And Koi in the Winter

Pond fish and koi are able to overwinter in a pond that has a 42”-48” depth (or more) at it deepest point; as long as there is a pond heater and aeration supplied.

For ponds that are less than 42”, fish can be brought indoors and kept in a holding basin with aeration and filtration.

How to Winterize a Pond and My Deicer

A Pond Heater is used to keep a small hole in the ice through the cooler weather when a pond would usually freeze over entirely.

It is not used to heat an entire pond, as this is unnecessary.

A small opening must remain in the ice to allow for the release of harmful gases.

Pond Aeration Specifically for Winterizing a Pond

An aerator allows for an increase of oxygen in the water over winter months, hot summer months and at night when oxygen levels are generally lower.

Your pond and fish are dependent on oxygen and with low running costs; it makes sense to run your aerator all year round.

Step 1: Cold Water Beneficial Bacteria

Begin Using Cold Water Bacteria once the water temperature has dropped below 50°F/10°C. This will aid in breaking down debris and sludge before winter sets in.

Step 2: Change Fish Food

Once water temperatures have reached 50°F/10°C change to a Fall/Spring food that has a higher wheat germ content that is easier for the fish to digest in cooler temperatures.

Stop feeding the fish all together once the temperature has reached 45°F (7°C).

Step 3: Take care of Pond Plants

All Hardy water lilies and submersible plants (parrot’s feather) can be dropped down to the deepest point in the pond for the winter.

Cut back any foliage from the lilies to limit decaying matter in the pond. Floating plants like hyacinth and water lettuce can be removed and disposed of.

Hardy marginals can be trimmed back, leaving approximately 2-4” of the plant from the base.

Tropical water plants should be brought indoors in a sunny area and treated as a house plant, always keeping the soil moist or a tray of water beneath.

Step 4: Pond Aeration

Move air stones from the deepest region of the pond to half the depth of the pond or 2’ from the bottom for the winter.

The air stones should not be near the fish or at the bottom of the pond, as they will transfer cooler air to where the fish are.

Step 5: Pond Vacuum Time!

If there are any loose leaves or debris in the pond, remove with a skimmer or pond net before the fish begin to go dormant.

The less waste left in the pond over winter the better for the safety of the fish. A Pond Vacuum can also be used to clean the bottom debris from the pond.

After the pond is clean, cover the pond with a net before the autumn leaves fall. This will save you a lot work removing the leaves by hand.

Step 6: Attention to Pond Pumps

Turn off, clean and store all pumps indoors in a pail or container of water; this prevents the seals on the pump(s) from drying out. Be mindful of your pond waterfalls as well!

If your pond is 4’ or deeper the pumps can be left at the bottom of the pond as an option.

Step 7: Pond Lighting - On or Off?

Remove underwater lighting before any freeze occurs or if your pond is 4’ or deeper submersible lighting can be lowered to the bottom of the pond.

Step 8: Pond Filters or Additional UV Systems

Remove the pressurized pond filter and do a thorough clean out of all the media. Store the entire unit indoors to prevent cracking/damage to the unit.

Also, remove any additional UV systems from the pond and store indoors.

This is a good time to check if the UV bulb and/or filter media needs replacing for the upcoming spring and to clean the quartz tube housing.

Pond Ionizers Care

Bring the head of the Ionizer in for the winter (the threaded part with the anodes) and clean off the anodes so they are prepped for spring.

Step 10: Pond Deicer and/or Pond Heater

Before the water’s surface freezes over entirely, float a deicer/heater towards the middle of the pond or over the deepest area of the pond.

Throughout the winter you will be able to see the LED light on the heater and know that your heater is working.

Final Recommendations and Thoughts

It is not recommend to have moving water or a pump running in the winter.

This will bother or disturb the fish by shifting the cooler water on top to the bottom where the fish should not be disturbed.