Winterizing Your Garden Pond

How to Care for Water Plants and Fish to Help Them Survive the Winter in Good Health?

Winter poses a challenge for outdoor ponds, their inhabitants, and aquatic plants. Proper preparation is essential to ensure that fish and plants survive the cold season without harm. Here's a step-by-step guide on how to care for your pond during the winter months.

Preparing Fish for Winter

Fish naturally slow down their metabolism in colder water. When the water temperature drops below 10°C, they stop eating and settle to the bottom of the pond, where they enter a state of dormancy.

Stop feeding when the water temperature drops below 10°C - uneaten food would only pollute the water
Check the health of the fish before winter - weak or sick fish are less likely to survive
Ensure sufficient depth - the pond should be at least 80-120 cm deep so that the bottom doesn't freeze
Maintain water quality - remove fallen leaves and organic debris that could decompose and release harmful gases

Pond Aeration in Winter

One of the biggest risks is the complete freezing of the pond surface, which prevents gas exchange. Toxic gases such as methane and hydrogen sulfide can accumulate under the ice, which is dangerous for fish.

Use a pond aerator or de-icer to maintain an open area on the water surface
Never break the ice by force - shock waves can harm the fish
If you don't have technical equipment, you can place a ball or piece of polystyrene on the water surface that moves slightly with the wind

Winter Care for Water Plants

Different aquatic plants have different requirements for overwintering:

Hardy plants (e.g., water lilies, pond reeds):

Cut back above-water parts after they wilt
Move containers to the deeper part of the pond (below the frost line)
They will survive the winter at the bottom without special care

Tropical and sensitive plants (e.g., water hyacinth, water lettuce):

Remove them from the pond before the first frost
Overwinter them indoors in an aquarium or container with water at temperatures around 15-20°C
Provide them with sufficient light

Floating and oxygenating plants:

Most species die off in winter but regenerate from spores in spring
Some species (e.g., hornwort) sink to the bottom and survive there

Pond Maintenance During Winter

Remove leaves and debris before winter sets in
Reduce or turn off filtration - in very cold conditions, it can cause excessive cooling
Check the pond regularly - monitor the open surface area and the condition of the fish (if visible)
Don't disturb the fish - avoid unnecessary disturbances that would force them to expend energy

Spring Restart

When temperatures start to rise in spring:

Gradually start the filtration system
Begin feeding only when the water temperature consistently exceeds 10°C
Return tropical plants to the pond after the last frost
Perform a water test and adjust parameters if necessary

Proper winter preparation is key to ensuring that your pond, fish, and plants wake up healthy in spring and continue to thrive throughout the new season.

Do you have a pond in your garden? Before the frosts arrive, give it some care. While some plants can rest peacefully through winter at the bottom, water lilies will need warmth!

There are two types of aquatic plants. You don't need to worry about frost-resistant aquatic and marsh plants if your pond is deep enough. At a depth of around 50 cm, they should be fine even in hard frosts.

With heat-loving plants, such as popular tropical water lilies and water hyacinths, it's the opposite. Before the frosts arrive, it's better to remove them from the pond, place them in a container with water, and keep them through winter at temperatures ranging from 15 degrees up to normal room temperature indoors.

If you keep fish from a climate zone similar to ours, there shouldn't be a problem, provided your pond is at least one metre deep and has a sandy or muddy bottom where they can hide. They'll safely overwinter at the bottom. The same applies to aquatic turtles (e.g. red-eared slider).

In any case, clean the pond in autumn – use a net to collect fallen leaves and plant debris – and don't let it freeze over.

Why?

If fish and turtles are overwintering in the pond, they will suffocate.
When prolonged hard frosts arrive, the surface will freeze too much and the ice will destroy even frost-resistant plants at the bottom.

What to do to prevent the surface from freezing?

If dried plant stems are sticking out of the pond, never cut them off before winter – they will create natural ventilation holes.
Put branches or some straw in the water.
If the surface does freeze over, break it up. Carefully cut a hole, or pour hot water over the ice.