How To Keep Pond Water Cool In Summer

Garden ponds can heat up quickly during the hot summer months, causing evaporation, algae blooms and making the pond environment uncomfortable for your fish.

Here are 7 easy ways to cool your pond water during hot weather. Following these steps will ensure that your fish have a healthy and comfortable pond environment during the summer months.

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Pond plants for shade

How do you know if your pond water is too warm?

The easiest way is to use a pond thermometer to check the temperature of the water.

Koi can tolerate temperatures between 35 and 85 Fahrenheit (1 to 29 Celsius) but the ideal temperature range is between 65 and 75 F (18 to 23 C). [1]

Warm water has a reduced ability to hold oxygen, so if you see your fish looking distressed and gasping for air at the surface of the pond, it could be a sign that the water is too warm.


Shading the Pond

One of the easiest ways to keep your pond water cool is by shading the pond.

You can install a shade sail over the pond to block out the sun’s rays or use a small tarp to cover part of the pond.

Pond plants with large leaves are also great for providing shade. Some good choices are water lilies, with their large circular leaves, or water lettuce, which floats on the surface of the pond.

Water lettuce

Pond Aeration

A small bubbler, fountain or waterfall helps to provide the oxygen needed for a healthy fish pond.

Pond aeration provides gas exchange at the surface of the water, which expels ammonia and increases oxygen levels in the water.

Aeration also brings cool water from the bottom of the pond up to the top.

Pond aeration

Pond Cleaning

Decomposing leaves and other debris can cause dangerous gases like ammonia to be produced in the pond.

These gases can be fatal for fish, especially in hot weather, so it’s important to scoop out any dead leaves, weeds and flowers before they have a chance to decay.

During hot weather you can also cut back on the amount of food you feed your fish.

The uneaten food will rot and cause the water quality to deteriorate.

If the fish are hungry they can eat the algae that flourish during the summer.

Water Change

Draining 10 to 20% of the pond water and replacing it with cool, fresh water is another way to cool down the pond water.

This is something you can do regularly during the summer months.

It’s not a good idea to replace too much pond water at once and I wouldn’t recommend adding big blocks of ice to the pond either.

This can alter the temperature of the pond too rapidly and shock the fish.

If your water is chlorinated, you’ll need to dechlorinate any new water that you add to the pond.

Create a Fish Cave

A fish cave is a place where fish can retreat to during hot weather and they’re a great place for fish to hide from predators.

You can make your own fish cave by leaning a few large flat rocks at an angle against the edge of the pond or place a hollow log on the bottom of the pond.

You can also buy ready-made fish caves like the koi kastle that your fish will love.

Fish pond

Pond Tint

Using a blue colored pond tint helps to shade the pond water from harsh sunlight while also reducing the visibility of your fish to predators.

Pond tint also gives your pond water a healthy blue appearance.

Pond Depth

Shallow ponds can heat up very quickly when the weather is warm so it’s best if your pond is at least 2 feet (60 cm) deep.

The water at the bottom of the pond is much cooler than at the surface so the fish can retreat to the lower levels as temperatures increase.

Garden pond edging

So there are my tips for keeping your pond cool during the hot summer months.

Warm temperatures can pose a lot of challenges for pond owners, but with some preparation you can ensure that your fish stay healthy during summer.


Do you have any questions about keeping pond water cool? Let me know in the comments below.

Are you on Pinterest? I have boards dedicated to Garden Ponds and Water Gardens that you may enjoy.

Keeping your pond cool during summer

Kelly Martin

Hi, I'm Kelly Martin, a landscape gardener with a special interest in ponds and water gardens. For over a decade, I've been designing and creating beautiful gardens that feature stunning water features, from small garden ponds to large water gardens. Read more

This Post Has One Comment

  1. Cindy grisham

    I have a 1/4 acre pond and we really enjoy swimming in it the only issue is that the water is super warm. It’s also 14ft deep in the middle. Other than putting plants in the water. Like is there an electronic pond chiller that would cool the water? Open to most any idea. Thanks Cindy

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