Sun on blue sky surrounded by clouds

The sun is out, and pond season is in full swing! As you probably know, koi are considered cold-water fish, so they need to stay cool and healthy during the summer months when temperatures rise.

Keeping your pond cool can be challenging, especially in hotter climate zones. Providing shade covering, oxygenating the water, and making sure your pond is deep enough to regulate the temperature will help protect your koi and your pond’s overall ecosystem from overheating when the temperature soars.

How Hot is Too Hot?

A hot pond can be dangerous for your koi since, unlike humans, they can’t just jump out of the water and cool off in an air-conditioned space. If the pond gets too hot, your koi can lose out on essential nutrients in your pond’s ecosystem. Plus, warm water holds less dissolved oxygen than cooler water, which is particularly dangerous in summer when fish are more active and require more oxygen.

Though koi can survive a wide range of water temperatures (between 35°F and 85°F), the ideal temperature is between 65°F and 75°F. Once your water temperature creeps past 75°F, it’s time to take some steps to cool down your pond. Investing in a pond thermometer is the best way to tell if the water in your pond is nearing an unsafe temperature for your koi’s health.

Invest in Shade

There are many tips, tricks, and tools to keep your pond water cool, but not even the fanciest gadgets will work as well as plain old shade. Plants, like water lilies and hyacinths, support your pond’s oxygen levels and provide excellent and easy shade coverage to keep your koi and other wildlife cool. Aim to have between one-third and one-half of your pond filled with aquatic plants in hotter regions.

Another highly versatile option for shading your pond is to install a shade sail. Shade sails are large pieces of tightly woven polyethylene fabric between multiple anchor points. Some sails are permanently affixed, while other shade sail systems allow for retraction. In addition to providing shade during hot summer months, shade sails can also provide year-round coverage from predators looking to make a meal of your koi.

Add a Water Feature

Adding a water feature to your pond is a great way to keep your pond aerated and your koi breathing healthy, oxygenated water in warmer months. Water features, such as waterfalls or fountains, constantly circulate water, which helps keep the water temperatures down.

Water features also help support optimal water conditions in your pond. During the day, aquatic plants in your pond are able to absorb helpful nutrients from the sun. However, when the sun sets, the plants begin to compete with your fish to absorb nutrients and oxygen from your pond water, making your pond vulnerable to a host of issues.

Do a Water Change

Performing a water change is an effective way to lower the temperature in your pond quickly. However, be careful with this tactic because drastic temperature swings can harm your koi.

In general, the recommendation is to replace 10-20% of your pond water volume once per week. The amount and frequency of water changes can vary depending on the number of fish in your pond, your geographic region, and your filtration system.

In addition to cooling your pond, water changes are particularly important in the summer months when koi produce more waste and debris from blossoming vegetation can quickly disrupt optimal water parameters.

Increase Pond Depth

Pond depth is a crucial element of pond design that drastically affects water temperature. A deeper pond will warm more slowly and protect your koi from the sun. A shallow pond can create a host of issues, including vulnerability to more drastic temperature changes.

If you’re still in the planning phase of building your pond, carefully consider how deep to dig your pond. The general rule of thumb is that your pond should be at least three feet deep, but it may need to be deeper depending on the number of fish you plan to have and your geographic region.

Of course, renovating an existing pond is a more challenging task. The first step is to relocate your pond inhabitants to a temporary home. Then you’ll need to drain your pond and remove any plants, rocks, and pond liners. From this point, you can alter the footprint of your pond however you’d like. Remember to consult with your local utility companies before digging to ensure you don’t endanger any utility lines.

The Moral of the Story

It’s hard to keep cool during the summer months. If it’s too hot for a person to be outside for an extended period, it’s also probably too hot for the fish in your pond without proper care and cooling methods. Keep your koi in the shade, keep your water fresh and aerated, and adapt your water-change schedule to fit the season. Remember that the shallower the pond, the more susceptible it will be to overheating. With the proper preparation and care, both you and your koi can stay chilled out this summer.

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