Pool Care Pool Troubleshooting

Does Solar Pool Cover Grow Algae In Your Pool?

Do Solar Pool Covers Cause Algae

Pool covers help us keep debris and leaves out and cut down on general swimming pool maintenance. A solar pool cover offers these benefits and a couple more. It can help heat the pool water, keep it warm and reduce evaporation. Besides providing these purposes, there is a trending question – do solar pool covers cause algae?

No! The best solar pool cover warms the pool water, protects the pool against pool debris and UV rays. It does not contribute to algae growth directly. However, if it had algae on it or if your pool water had algae spores, the water warming could increase their progression, especially if there are phosphates in the water.

Solar pool covers bring a lot of benefits to your pool. And even though they can indirectly contribute to algae growth, there are measures you can take to prevent algae presence in your water. This post will take you through some of these preventive measures.

How Does A Solar Pool Cover Contribute To Algae Growth?

A solar pool cover is mainly designed to serve as a solar energy transfer blanket that allows the solar energy from the sun to pass through it and trap it inside the pool. When trapped, it heats the pool water and protects the heat from getting lost. The water surface covering also helps prevent water evaporation while also keeping the debris and leaves out.

According to OSU College of Agricultural Sciences, algae growth is best when the bacteria received 10-15 hours of sunlight daily and if the water temperature stays anywhere between 60-80° Fahrenheit. So, a solar pool cover won’t cause algae in your swimming pool. However, since it can warm the water by 8 degrees on a hot day, of the other conditions staying right, your solar pool cover could rapidly accelerate the algae. In hours you could be dealing with full-grown algae.

That could double if your pool chlorine levels are low, water pH is high, and phosphate present in the water.

  •  Phosphate is the food for algae
  • Chlorine is the sanitizer when low; then your swimming isn’t protected.
  • When the water pH is high, the chlorine effectiveness is affected

But there is some good news; the next section gives you a series of things you can do to prevent algae growth when you’re using a solar pool cover.

What Can You Do To Prevent Algae Growth When Using Solar Cover

A solar pool cover brings us many benefits, including pool water warming, debris protection, and evaporation prevention. And since it does not contribute to algae growth directly, its specific conditions boost the algae growth. But if you did the following, you could prevent these from happening in your swimming pool.

Use the Right Solar Cover

One way solar could increase algae growth is by allowing sunlight to pass through to the pool water and affecting the chlorine levels. When reduced, the pool gets exposed to the algae spores, and they start to grow.

If you have an algae problem and it has become a recurring issue for you, you might be living in an area with temperatures favoring their growth. And the solar pool cover acts as their growth booster.

The best cover for you would be a bubbled solar blanket with a clear top and Dark on the bottom. The clear top allows the energy through while the dark bottom absorbs heat and transfers it. It’s excellent in retains heat well.

It doesn’t allow much sunlight to pass through, though. It acts by transferring the heat through the water.

Clean the Cover Before Use

If you only get alga when you use a solar pool cover and they mostly start to appear after two weeks or so, it’s the most likely culprit. It’d be your cover is introducing the algae or algae spores. When the water gets warm, they start to grow and deplete chlorine.

The best solution here is to clean the solar cover using a cover cleaner. The cleaner kills the spores and leaves the solar pool cover clean. Avoid using bleach that you use to clean the floors or clothes before laying it on your pool, as it could detoriate your pool cover or void the warranty. But make sure the ppm of chlorine in the bleach is less than three, or it could damage your pool cover.

Keep the Water Moving

Algae love stagnant water; they strive in them. And you might be tempted to turn off the pool after covering the swimming pool with a solar pool cover. But DON’T.

IF you’re worried about whether it’s safe to run a pool pump when the cover is on, the good news is, it’s all safe. Run the pump as often as you can to keep the water moving. A variable-speed pump allows constant water flow without high energy usage.

Run your pool filter regularly; give it two separate 1-hour cycles each day. You could set a timer to run during the night. That way, you can take advantage of your off-peak electricity rates.

Keep the Pool Cover Clean

Even though it’s never a good idea to use a solar pool cover as a protective pool cover, at times, you might leave it too long to collect a lot of debris.

The leaves and debris could become too heavy for the solar cover and start tearing it or even cause it to sink in your pool. If that were to happen, it risks your swimming pool in getting pool algae.

The debris, dirt, and pollen could also disintegrate, and before you know it, they have turned into mush and sludge.

If it was to rain, all these could be washed into the pool water as a semi-liquid and become food for algae or even introduce algae spores.

When using a solar cover, try to keep it clean and free of debris and leaves. If you’re planning not to use the swimming for more than a week, the best action would be closing it with a pool safety cover.

Keep the water chemistry balanced

One of the necessary conditions for algae growth is imbalanced pool chemistry. A slight drop in chlorine could turn your swimming pool into a partying ground for the green algae.

Even if you’re not using your pool, the pool chemistry could be upset by rainwater, run-off water, bugs, vegetation, and any other contaminant that could find its way in the swimming pool.

You need to test your pool water frequently. You can use the simple-to-use pool test strips, pool testing liquid kit, digital pool tester, or take a sample to a pool store.

Chemical levels of balanced pool water should be at:

Chlorine1-3 ppm
pH7.2 – 7.6
Calcium200 ppm
Alkalinity80-100 ppm
Cyanuric Acid30-50 ppm

If you get anything below these levels. It’d be best to balance it immediately and significantly before using the pool cover.

Remember, even though strong chlorine is the ultimate controller for pool algae, high levels above three ppm could start to erode your solar cover.

Shock Your Pool Regularly

Pool Shock is mostly the best way to kill pool algae. It’s primarily applicable when you notice you have algae in your pool.

You could take the measure to protect your pool against the algae spores that might have found their way into your swimming pool waters.

If your pool water stays are 50ᵒ and 70ᵒF, it’d be best to shock it after every three weeks. If the water temperature stays above 70ᵒF, the best shocking interval would be 7-14 days.

After shocking your pool, run the filter for at least 6-hours to make sure all the chemicals are distributed throughout the swimming pool evenly.

It’s also best to shock your pool at night. If you do it during the day, the scorching sun could act on the chlorine levels reducing its effectiveness.

You must not use your solar cover after a shocking pool. Wait until the chlorine levels lower. The high chlorine concentration could erode your solar pool cover.

Monitor You Pool Regularly

Similar to how you monitor your pool during the winter, keep an eye on your pool surfaces using a solar pool cover. Because of the warm temperatures, pool algae tend to grow relatively fast.

If you start to notice some green mucky around the dark corner, yellow or brown stains around the pool stairs, or black sand-like staff on the pool floors, there could be algae in your pool. The best action at this point would be to shock your pool and add algaecide the following day.

Use Algae Starver

Another preventive measure that can allow you to get the full benefits of a solar pool cover is adding an algae starver.

As the name suggests, algae starver removes phosphate build-up in the pool water, which acts as algae food, thus starving it.

Once you add the chemical, run your pool filter for about 12-24 hours. That gives it time to run to all the pool corners removing the phosphates. When there no food, the algae dies.

Related Questions

Q: Should I Remove Solar Cover During the Day?

A: No! This the time when the solar pool cover heats the water by allowing the sunlight into the swimming pool and blocking it inside. However, if you live in those areas that get scorching heat during the day and extreme cold during the night, use it only.

Q: Does a Pool Heat Up Faster With The Solar Cover On?

A: Of course, YES. According to most pool owners, pools get warmer faster after installing a solar cover by trapping the warmth. That can even save you on heating bills, and you can use the electricity for something else.

Q: Can You Cut a Solar Pool Cover to Size?

A: Yes. If you have ever used a solar pool cover, you could have seen the ends aren’t seamed. That means they make is leaving the allowance for you to adjust to fit your pool size. You can cut it 3-5 cm over the pool edges up the tiles to ensure it stays below the pool rim using a pair of household scissors. However, keep in mind that the solar covers are soft, and it’s easy to cut too much.


Do solar pool covers cause algae? No, pool cover warms the water, keeps the pool water warm, protects against evaporation, and more, but not causing algae growth. However, when it heats the water, it could increase the development of the already-in-the-pool algae.

The algae could also attach itself to the solar cover, and you could introduce it when installing the pool cover. The best control is to regularly shock the pool, clean the solar cover before use, and discuss the rest.

About the author

Sharif Miah

Hi! I'm Sharif, the founder of Globo Pool® and I have been working in the pool & hot tub industry for the last few years. I love to share my experiences with people & hope you are enjoying my information and lessons!

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