How to Heat a Pond in Winter


If you have a koi fish pond in your backyard, there are quite a few things to keep an eye on. This includes the temperature of the pond throughout the year.

Of course, this is largely because of the fish inside the pond. Koi thrive in water warmer than 48 degrees Fahrenheit and it’s essential for aspects of care like their feeding schedules.

Yet, the question comes down to how do you ensure something outside meets a certain temperature? Here, we’ll take a look at how to heat a pond in winter.

Starting Before Winter

There is something that you can do ahead of time to prepare your pond for heating in the winter. The answer is simply to routinely clean your pond before the season rolls in.

Pond in autumn

You’ll want to carefully remove organic debris, change out half of the pond water, and treat and purify the water. This will help make sure that you can primarily focus on keeping the water warm enough.

This will also help avoid any complications in heating the water as well. It even lowers the chance of your fish getting sick, affecting the pond’s optimal temperature.

An even more fundamental thing to watch out for, though, is pond depth. When you first install your pond, make sure it has the proper depth.

This will help you to give your fish a warmer depth to escape to since the surface is the coldest. On top of that, deeper ponds are less likely to freeze completely when met with freezing temperatures.

So, if you live in a colder climate where winters are harsher, you’ll want a deeper backyard pond. If freezing temperatures are a constant for winter in your climate, your pond should be at least four feet deep.

Using a Pond Heater

The easiest way to prepare your pond for cold weather and maintain a standard temperature is a pond de-icer. These devices are handy and almost as essential as a pond aerator or pond liner.

Electric pond de icer

There are a few different ways that you can use a pond heater, though. So, let’s take a second to break them down.

First, you can just set a regular temperature for your pond to maintain throughout the year. Then, it will do all the work for you.

To save money, you can opt for a temperature as low as 68 degrees Fahrenheit. However, the ideal temperature for a koi fish is closer to 68 degrees Fahrenheit.

Another idea is not to rely on the pond heater as a constant tool either. You can use the heater as an emergency tool instead.

Put another way, you can use your heater when you need it but keep it turned off otherwise.

Using a Pond Covering

Of course, the focus in this particular issue is on keeping the water in your pond warm enough. Yet, one of the best ways to do this is to have some control over the ambient air.

The easiest way to do this is to cover your pond. This works in much the same way that a greenhouse stays warm enough for plants to thrive.

During the day, the plastic covering will help trap heat from the sunlight. On the other hand, at night, the plastic covering will help to keep this warm air trapped inside the covering.

This also protects your pond from the chilly winds of winter. These openly blowing across your pond’s surface does a lot to bring the temperature of it lower than ideal.

Even if this isn’t your main method, it’s still a good one to understand and know. It’s great in a pinch if you lose power or your pond heater malfunctions.

How to Handle Snow

If you experience snow during the wintertime, you need to know how to handle that too. Specifically, how does snow on your pond relate to keeping the pond warm enough for fish?

Your first impulse may be to remove the snow or ice from the top of your pond entirely. After all, wouldn’t a cold substance on the water make the water colder?

On the contrary, there’s an argument for keeping the snow on as well. You don’t have to worry about snow or ice chilling the water further because it likely won’t.

Rather, the snow and ice that make up the surface of your pond can actually be insulating. By leaving it there, you’re protecting your pond from chilling winds and even regular fluctuations in temperature.

Although, in the case of ice, you may not want to remove the ice but still drill a hole. Since ice will seal your pond off, you don’t want toxic compounds for the fish trapped inside.

Frozen pond with red carps

A Note on Bringing Your Fish Inside

There’s an alternative to heating your pond completely if your main focus is heating for the safety of the fish. Of course, this also depends on what kind of fish you have.

The method is to skip on heating the pond entirely by bringing your fish inside. This only works with certain fish types, though, including oranda, pleco, and black moor species.

Yet, this method isn’t the most favored one. This is namely because it saves the fish without considering the needs of other elements of your pond like plant life.

All in all, while this is an option, it isn’t the best choice for your pond as a whole.


Heating your koi pond in the winter is a crucial part of routine maintenance and keeping your fish healthy. Furthermore, it works to help keep the other living components of your pond – like plants – healthy.

In the end, you have multiple options on how to heat your pond in preparation for winter. This gives you plenty of room to find what works for you.

From using a pond heater year-round to only when you need it or even another option, you have several choices. With these, you can make sure that your koi and pond are properly ready for winter.