How to Winterize Your Garden Pond

How to winterize the garden pond

It would help if you winterized your garden pond in good time in autumn before the first frosts arrive. It would be best to protect sensitive water plants, fish, and other pond inhabitants from sub-zero temperatures. If your plants and fish need to winter outside the pond, it depends on these creatures’ type and depth of your pond. If you make the pond clear in time for the winter, you can prevent damage to the pump and counteract the formation of putrefactive gases. A mud vacuum does an excellent job because, over time, mud has formed from dead plant matter, algae, fish droppings, and leaves that have fallen into the pond. You work more efficiently and safely with a mud vacuum than by hand and save time preparing the pond for the winter.

How can You Counteract the Formation of Foul Gases?

Digester gases can be a severe problem, as they can cause damage plants and death to fish and other animals in the pond. These gases can occur when organic matter such as fish feces, leaves, dead plant matter, or algae decompose. If the pond freezes over, there is a shortage of oxygen. The lack of water circulation exacerbates this problem – methane and hydrogen sulfide formed by the decomposition process, which then causes the water to tip over. If bubbles are already rising, the pond is too silted. To counteract sludge formation, remove dead leaves from water lilies and other aquatic plants, and fish out leaves and branches that have fallen into the pond. Sludge is the basis for the formation of putrid gases. If sludge has already formed, you should remove it with a sludge vacuum when preparing your pond for winter.

Bacteria pose another danger to fish and other animals in the pond. They take advantage of the lack of oxygen in the water and decompose dead plant matter. To avoid endangering your fish and other pond inhabitants, you should remove string algae and decomposed organic matter from the pond. You can protect your pond from falling leaves and branches by stretching a net over it. This net will help you counteract sludge formation, as less organic material will end up in the pond. If the trees no longer carry leaves, you can remove the net again.


If your pond is older and a thick layer of sludge has already formed on the bottom, you should remove about a third of the sludge. This sludge is good as organic fertilizer for your garden. If there are larger creatures in the mud, you should put them back into the pond.

Test if the Water Is Healthy

Preparing your pond for winter is an excellent time to check if the water is healthy. You can quickly determine this by stirring up bottom mud and then checking on the pond again after an hour or so. If the water is crystal clear, also after an hour, then the water is healthy. However, if the water remains cloudy, you should check and fix the causes. Turbid water can be caused by

  • too much fish food, which the fish did not eat
  • too many fish, which cause a lot of excrement that forms a food base for algae
  • leaves and other organic matter that has fallen into the water

You can eliminate these causes quickly. You can be more economical with the fish food. If the fish have multiplied a lot, you can give some fish to friends who also have a garden pond. There are also various swap meets for pond lovers where you can trade fish or aquatic plants. You should remove foliage from the pond regularly. Carp fish, which include goldfish, churn up the mud to look for food. Separate from some fish, the water will soon become clear again.

Prepare Your Aquatic Plants for the Winter

Aquatic plants are essential for the pond. They are simply part of fish and other marine animals’ habitat, as they provide a biological balance and release oxygen into the pond water. However, if the plants have increased, you will need to remove some of them. You should divide the plants. For plants in planting baskets, you can do this by removing the plants with a basket from the water, taking the plant out of the basket, and dividing it with a spade. You then put the plant back into the basket. If you planted the plants in the water without the basket, you might want to drain some water and then divide them with the spade.

In no case should you throw away the plants that you no longer need. You can still make other pond owners happy with it. Offer such aquatic plants at a swap meet, for example. It would help if you cut back strongly growing plants that spread quickly. You should cut the plants as far down as possible and take care not to hurt amphibians and fish that hide between the leaves. Cut off any dead plant parts generously. Cut plants that are at the edge of the pond in half. It would be best if you disposed of the cut plant parts in the compost.

Native aquatic plants are hardy and can overwinter in the pond. However, if you have delicate or exotic plants in your pond, you will need to take them out to continue to enjoy the next season. Such plants include tussock fern or water hyacinth. It would be best to store these plants indoors in a cold but frost-free place for the winter. If you would like to plant your pond with evergreen aquatic plants, a place that remains ice-free in winter is suitable for this. The plants can then produce oxygen even in winter. To provide the plants with enough sunlight, you should remove the snow from them.

What Should You Pay Attention to the Pond Pump?

Before the first frost comes, you should remove the pond pump from the garden pond so that it arrives through the cold season undamaged. You should clean the pond pump thoroughly to avoid corrosion and other damage. To prevent the pond pump seals from becoming brittle, you should store the pump in a container filled with water in a frost-free location. You should disassemble the filter system so that it does not get damaged. If you have lighting in your pond, disassemble it as well.

Frost Protection for the Garden Pond

If the garden pond is at least 30 inches deep, it will not freeze completely. For a shallower pond, you need to make sure that the water surface does not freeze completely. Since ice is much lighter than water, it always floats on the water surface. The layer of ice forms natural insulation and ensures that the pond does not freeze completely. If your pond were to freeze completely, it would be a death sentence for all of its inhabitants. If your pond has a depth of at least 30 inches, this is beneficial for the fish living in it. They will retreat to deeper areas where the water temperature is around 40 degrees Fahrenheit. If they are not sensitive fish such as breeding species of goldfish or koi carp, you do not then need to remove the fish from the pond over the winter.

Promote the Formation of Temperature Layers

When outside temperatures drop and the first frost sets in, different temperature layers form in the pond. At 40 degrees Fahrenheit, water has its most excellent density. It is then at the bottom of the pond. Towards the end of autumn, you should not clean the pond water. To not hinder the formation of layers, you should avoid circulating the water through the pond pump.

How to Overwinter Your Fish?

The body temperature of fish is not influenced by metabolism but by the environment. Many fish do not get into trouble with low ambient temperatures and can overwinter in the garden pond. Most fish stay awake at low temperatures, but they shut down their metabolism, so they are noticeably quiet. Only a few fish overwinter in a kind of dormant state – most fish stop feeding at temperatures as low as 50 degrees Fahrenheit. Therefore, you do not have to provide the fish in winter. The fish then feed on their fat reserves or microorganisms in the water. When the water temperature rises above 60 degrees Fahrenheit, you should feed your fish again. If you have sensitive fish such as koi in your garden pond, you should take them out before the cold sets in to be on the safe side. You can overwinter the fish in a tank of water in a cold, frost-free, dark place indoors.

How to Keep Your Pond Ice-free

If animals live in your garden pond, you should always keep the pond ice-free in one spot so they can survive the winter. An inexpensive solution is ice freeholders made of styrofoam with an aeration kit. They allow oxygen exchange between the air and water, as well as the escape of foul gases. Alternatively, you can use a pond heater. If you have neglected to take care of frost protection and the ice cover is already closed, you should melt a hole in the surface with hot water. Cracking the ice surface is not recommended, as aquatic life could be disturbed in their winter torpor. The resulting pressure wave can damage the swim bladder of the fish.


You should winterize your garden pond well before the first frost. You could divide plants that have increased and cut back plants that have thrived. Remove dead plant parts. If a layer of mud has formed in your pond, you should remove a third of it. A mud vacuum will make your job easier. Native aquatic plants that are not sensitive can overwinter in the pond, while you should remove sensitive and exotic plants from the pond. Fish can also spend the winter in the pond if they are not sensitive species, which you should winter in a water tank in a cold and dark place indoors. There must always be a spot in your pond free of ice so that putrefactive gases can escape, and there is a fair exchange of oxygen between the air and the water.

Florian Egert

I am Florian Egert, the owner of I live with my wife and two children in Germany in a small village in the countryside.

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