10 Tips for Protecting Fish from Summer Heat

Keeping pond healthy in summer, high temperatures
Who wouldn't want to enjoy a glass of lemonade next to the pond on a warm summer day?

Summer can be one of the best times of year to enjoy nature in your backyard. But extreme temperatures can put a damper on the fun - for both you and your pond life.

Here are 10 tips for keeping your fish and plants health in the summer heat:


At a Glance: Summer Pond Tips

  • Keep water oxygenated
  • Clear debris often
  • Don't overfeed fish
  • Watch water levels
  • Provide shade
  • Make sure your pond is at least 2 feet deep
  • Use biological filters and skimmers
  • Control algae
  • Keep predators away
  • Test your water

1. Make sure your fish can breathe

Pond Aerator

Pond Aeration Kit

Warm water holds less oxygen than cool water. At the same time, your fish are more active and consume more oxygen when temperatures rise. This combination can suffocate your fish if you don't help them out.

Consider installing an aerator to add some much-needed oxygen to the water for your finned friends. Aerators will also serve you during the winter by pumping oxygen into a partially frozen-over pond.

How can you tell if your fish aren't getting enough oxygen? Watch for behaviors like gasping at the surface of the water and congregating near waterfalls or fountains.

2. Clear debris often

Decaying leaves and fish waste are never good for your pond. This is especially true in the summer.

Organic materials give off ammonia as they break down, and excessive ammonia levels can kill pond fish. With fish already stressed in hot weather because of lower oxygen levels in the water, you don't want to make matters worse.

Regularly clear debris from your pond, ideally removing material like leaves and fish food before they sink to the bottom. A good skimmer system will make this job easier. If you don't have a skimmer, you have to do the work by-hand.

3. Don't overfeed fish

Koi pond ecosystemFeeding fish is one of the highlights of owning a pond in the summer. You can't feed them in the winter, so you might as well enjoy it while you can.

But you can have too much of a good thing.

Just like fish waste or dead leaves, any food your finned friends don't eat will sink to the bottom of your pond and decay. That means more harmful ammonia and less oxygen in your water for your fish.

Only feed fish as much as they will eat in a few minutes, and don't feed them more than one to three times each day. They also snack on mosquitos, plant matter and other thingsĀ  in your pond, so you don't need to worry about them not getting enough to eat.

Related: How often should I feed my fish?

4. Keep an eye on water levels

It's common sense: Water evaporates faster in the summer. Your pond might lose an inch or more of water each week when the sun beats down, especially if you have lots of splashing from waterfalls or fountains. Don't scramble for a leak repair kit if you notice a little water loss; just top off the pond with water from a garden hose and keep an eye on it. We recommend keeping a bottle of Pond Detox on-hand for these occasions. Pond Detox removes chlorine and other harmful chemicals from your tap water and is a must-have for those times when you forget to shut off your hose.

(If you continue to see significant water loss, follow our instructions for finding the source of the problem before you schedule a service visit.)

Summer also brings downpours and thunderstorms, so don't let your pond overflow. You don't want to chase fish down the sidewalk.

5. Provide shade for fish

WarliliesYour fish won't get sunburn. They will get hot in the sun.

Koi can survive in water temperatures up to 90 degrees - somewhere between lukewarm and the temperature of a hot tub. That does't mean, though, that they will thrive in such an environment.

Plants like waterlilies, lotus and water hyacinths can provide great shade cover for your pond and help keep water temperatures down. They also hide your fish from predators that might look to your pond for a quick snack.

Aim to cover between one-third and one-half of your pond's surface with aquatic plants. Not only will your fish thank you for the shade, but you'll have an easier time controlling string algae thanks to the increased nitrate uptake.

Check out ideas for adding plants to your pond

6. Make sure your pond is deep enough

Deep water holds a steadier temperature than shallow water. If you have a very shallow pond - with a maximum depth under 2 feet - consider investing in an upgrade. The deeper water will stay cooler in the summer and warmer in the winter.

Deeper water also gives you the option to add larger fish like koi, which need the space to exercise their vertical swimming muscles.

7. Use biological filters and skimmers

A well designed pond will serve you well in any temperature.

Biological filters pull in water from your pond and circulate it through a series of materials that have lots of nooks and crannies where beneficial bacteria colonize. These bacteria keep ammonia levels down and help prevent algae - two things that keep your water healthy year-round.

Skimmers also play a crucial role in maintaining your pond's ecosystem in all temperatures. These filters remove physical debris from your pond, much like a pool skimmer, and save you the trouble of pulling gunk out with a net. Less debris means less stuff decaying in the bottom of your pond, which means healthier water.

8. Control algae

Algae usually thrive in the springtime, before beneficial bacteria have a chance to recolonize after their winter nap, but issues can persist into the summer.

String algae feed on nitrates in your water, so you can starve them by adding a variety of nitrate-eating plants. Single-cell algae - the kind that turns your water green - eat nitrites, which you can keep at a minimum by filling your pond with nitrite-chomping bacteria.

The good news about algae is it very rarely poses a danger to fish. They don't mind green water, and having a little bit of stringy or fuzzy algae in your pond is actually a sign of a healthy ecosystem.

9. Watch out for predators

Your fish aren't the only animals with a little more energy during the summer.

Predators like heron and raccoons will often take advantage of the warm weather to treat your pond like an all-you-can-eat sushi buffet. Because your fish were selectively bred for pretty colors, not camouflage, they can become easy pickings.

Make sure you have plenty of fish caves and other places where pond pets can hide, and invest in humane predator deterrents.

10. Test your water

If your fish are acting funny - not moving much, swimming in unusual ways or even dying - look into getting your pond water tested. The decreased oxygen throughout the summer can throw off the chemical balance of your pond.

If you live near York, PA, all you have to do is put a small water sample in a container and bring it to our store. We can test ammonia, pH and other levels in just a few minutes.

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