The Pond is Heating Up!
For the last 3 days (written on July 15, 2026) out pond water temperature has gotten as hot as 85°F. While this is a normal part of the summer, we need to be aware of pond temperature. As the pond water begins approaching 90°F, we can help. Here is what you need to know about your pond temperature.
Aeration
As water warms, it holds less dissolved oxygen. Both fish and beneficial bacteria(also a living thing) require more oxygen in warmer weather because their metabolism speeds up. That’s why extremely warm water can become stressful for fish, especially during long periods of hot weather. If you don’t have an aerator – get one!
Here is a picture from today of our Biofall and stream. The Impatiens, Water Hyacinths and Water Lettuce , Forget Me Nots, Obedient plant and the Aquatic Hibiscus are all in the water! You will notice we have some string algae. Yep, we do. Not in the pond at all just the stream. We can remove it, but I am not too worried about it.
Help Keep the Pond Cool
- Keep waterfalls and aeration running. They greatly increase oxygen levels, which is often the most important factor during hot weather. Aeration does bring the water temperatures down a little too!
- Increase shade. Quick ways to increase shade are to move a patio umbrella close to the pond. You could add a shade sail, but I think that is a bit of work! If you are desperate, you can even put those garage floor mats (clean ones) right on the water!
- Add water lilies and floating plants. Their leaves provide natural shade and reduce how much sunlight reaches the water. But let’s be honest here, it takes time for them to grow. So just adding them today won’t solve your problem immeidately!
We have used these black mats for several things in the pond. They float, they are cheap and they provide more shade of the pond needs it! You can see the white lines that we had up at the time (fishing line). We had that up to help deter the very persistent heron.
- Top off with cooler water if needed. If you are new to Colorado, you may not know this, but when you run the hose and first let the water that was heated up to a million degrees out first, the water will come in COLD! Yes! SO, if the pond temperature is approaching 90°F, replacing about 3–4 inches of pond water with fresh, cool hose water can help lower the temperature. Always remember to treat the new water with a dechlorinator (if you are using city hose water).
- Avoid overfeeding fish. If your pond temperatures reach 90°F, don’t feed the fish. Fish eat less in extreme heat, and uneaten food can reduce water quality and oxygen levels. Let me be really clear here, too much uneaten food when the pond water is 90°F or above can lower oxygen levels and KILL THE FISH!
- Remove excess algae and debris. Decomposing organic matter consumes oxygen. YES! SO get it out!
Avoid
- Adding a large volume of COLD HOSE water into a hot pond all at once. Sudden temperature changes can stress fish. So – above I said add 3 to 4 inches, not a whole foot or more!
- Turning off your aerators or waterfall overnight. Please. Fish experience their lowest oxygen levels just before sunrise, making nighttime aeration especially important.
Look at the Chordata Chameleon on the right – they are looking so good! The water lilies in this picture are Miniature! The light yellow flowers are about 1 1/2″ diameter. They are really nice in a smaller pond where there is not a lot of depth.
Kristi's Tips
If you put out a patio umbrella, be aware of wind. These things blow right over! Put a heavy rock on the base.
When you are tending to your pond on a hot day like this, wear a hat and GET IN THE POND! I like to wear flip flops and go into to about the bottom of my shorts while I tend to the plants. Feed your fish a slice of watermelon! They may take a few minutes to figure it out but they love it! Don’t forget to remove the rind later.
* This blog was NOT written by AI. This was written by me. I am not a professional writer, I am a pond person. Therefore, if you see a typo, please forgive me!
*No koi were harmed in the making of this content.