How do I know if my koi are short on oxygen?

Watch them early in the morning. Koi gasping or hanging at the surface, crowding near the waterfall, or moving sluggishly after a hot night are the classic signs. If you see it, increase circulation and add aeration right away, stop feeding for the day, and remove any decaying algae or uneaten food.

Should I add cold tap water to cool my pond during a heat wave?

Be careful. A large dose of cold tap water can shock fish with a sudden temperature swing, and city water contains chlorine or chloramine that harms fish and beneficial bacteria. Top off small amounts with a dechlorinator, or use an auto-fill valve paired with a dechlorinator, and rely on shade and aeration to cool the water.

How much does pond aeration cost for a backyard koi pond?

Backyard pond aeration systems run roughly $3,200 to $7,360 depending on pond size and the system. A bottom diffused system puts a compressor on shore and diffusers on the pond floor, which mixes cooler bottom water with warmer surface water and keeps oxygen up through the night.

Do koi need shade in a Massachusetts summer?

Yes. Aim to shade roughly a third of the surface with water lilies, floating plants, or a nearby tree or shade sail. Shade lowers water temperature, cuts the sunlight algae need, and gives koi cover from herons. Plants do double duty because they also take up the nutrients that feed summer algae blooms.

How to Keep Your Koi Safe During a Heat Wave | New England Aquatic Landscaping

Summertime brings longer days, more sunlight, and unfortunately for pond owners, rising water temperatures. When extreme heat hits, your koi can become stressed, vulnerable to illness, and even suffer from oxygen depletion. Here’s how to protect your fish and keep your pond healthy during a heat wave.

1. Monitor Water Temperatures

Koi thrive best in water temperatures between 65°F and 75°F. Once temperatures creep above that range, especially past 75°F, your pond’s environment becomes more stressful for your fish. Use a floating thermometer to keep tabs on temperature regularly. If it starts to climb, it’s time to take cooling action.

2. Add Shade

Excess sun exposure raises water temperatures and stresses your koi. One simple way to help? Add shade. Install a shade sail or use aquatic plants like water lilies or hyacinths. These not only provide cover from the sun but also help maintain cooler water and reduce algae growth.

3. Check Oxygen Levels

Warm water holds less dissolved oxygen, and that spells trouble for koi. If your pond doesn’t already have an aeration system, now’s the time to install one. Diffused air systems or surface aerators will help keep oxygen flowing when your fish need it most.

4. Adjust Feeding

Koi metabolism changes with temperature. When the water reaches 85°F, your koi may struggle to digest food properly. Feed lightly, and once the temperature hits 90°F, it’s best to stop feeding altogether. Unused food will only break down and add to water quality issues.

5. Remove Excess Algae

A bit of algae is natural, but too much during a heat wave can strip oxygen from your water, especially overnight when photosynthesis stops. Keep algae in check with manual removal, and consider adding beneficial bacteria to outcompete unwanted growth.

At New England Aquatic Landscaping, we specialize in creating and maintaining koi ponds designed to thrive in every season, even the sweltering ones. Whether you’re looking to add shade, install aeration, or schedule a summer maintenance checkup, we’re here to help.

Need help protecting your pond this summer? Contact us for expert service and advice.

Shawn Cutroni

Founder & Co-Owner, Master Certified Aquascape Contractor

Shawn Cutroni founded New England Aquatic Landscaping in 2008 after a backyard pond he built for his mother as a Christmas gift turned green within weeks. He spent the years that followed learning the biology, filtration and stone work that let a water feature sustain itself, became a Master Certified Aquascape Contractor, and rebuilt that first pond. Today he leads NEAL's construction, maintenance and office teams from Cherry Valley, Massachusetts, designing, building and servicing ecosystem ponds, koi ponds, pondless waterfalls and natural swimming ponds across New England. He also hosts the I Love Ponds YouTube channel, where he documents builds and answers pond owners' questions.

More about Shawn and the NEAL team

How to Keep Your Koi Safe During a Heat Wave

1. Monitor Water Temperatures

2. Add Shade

3. Check Oxygen Levels

4. Adjust Feeding

5. Remove Excess Algae

Shawn Cutroni

Koi Ponds

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