We earn commissions from purchases

Do Solar Pool Covers Cause or Prevent Algae? How To Avoid Green Pools

If you notice your pool water turning a green color, then it’s most likely due to the presence of green algae. While algae is always present in some amount, it can develop resistance to normal chlorine dosages, and if the circumstances are right, it can take over in a very short time.

Since pool covers heat up your water, you may rightly wonder – do solar pool covers cause or prevent algae?

What Causes Green Algae in Water?

Research has shown that algae growth in pools is at its highest when the pool water receives up to 10-15 hours of sunlight, coupled with the water temperature being between the ranges of 60-80° Fahrenheit.

solar pool cover with reels

This shows that, while a solar pool cover won’t by itself cause green algae to be present in your pool water, if the water or pool cover already had spores, the increase of the water temperature could rapidly increase algae’s spread and turn the pool green.

The risk is even greater when the chemical balance of the water is awry. This could occur when the phosphate level is high or when the chlorine level is low.

How To Prevent Algae Growth When Using Solar Covers?

Considering how efficient are solar pool covers and the benefits that a solar blanket gives, such as prevention of heat loss, reducing energy costs, preventing evaporation, and so on, it doesn’t make sense to ditch one just because of algae.

So how can you prevent algae growth even when using solar covers?

Try doing the following:

Use the Correct Type of Cover

If you want to avoid having a green pool, one of your best options would be to buy a bubbled solar blanket with an opaque cover at the bottom and a clear top. The opaque bottom absorbs heat and retains it, while the clear top allows the energy to pass through.

Using some of the best solar pool rings is another option, they have the advantage of reducing the growth of algae since they are not covering the whole surface.

Also, ensure that your swimming pool cover is of the right size and shape for your pool, as this goes a long way in ensuring that your swimming pool water is well-covered and does not allow sunlight to pass through.

You should also use the right pool cover reel, either a DIY solar cover reel or a ready-made reel to help you keep your pool area organized, protect your pool cover, and make it easier to position and store the cover.

Kill the Algae Food

One of the best ways of preventing algae growth is by killing their food source, i.e., phosphate. You can get rid of phosphate build-up with the aid of an algae starver.

You may then filter the pool for a longer period to remove the already existing algae spores. This will ensure that there’s no food for algae to feed and thrive on in the clean pool.

Use a Clean Cover

As a pool owner, always keep an eye on the solar cover and keep it clean and free of debris and leaves. Do not leave your solar blanket lying around long enough for it to collect a lot of debris.

This can be easily washed into the water, introduce algae spores into it, and before long, transform it into a green pool. You can ensure that you keep your cover clean by using a leaf blower or a leaf rake to get fallen leaves away from the area.

A pool vacuum hose may also be used in keeping other debris away from the pool. Check our guide on how to clean pool cover.

Regularly Shock Your Pool

If you notice that you already have an infestation of algae, one of the best measures that you can take to get rid of them is by shocking your pool. Don’t worry, you wouldn’t be electrocuting your pool.

What this means is that you’ll be adding chlorine or non-chlorine sanitizing chemicals to your pool. The goal is to raise the free chlorine level in the pool water so that the sanitizer has greater power to eliminate algae, germs, and chloramines.

To ensure that all of the chemicals have been distributed throughout the swimming pool equally after shocking it, run the filter for at least 6 hours. It’s also crucial to shock your pool at night.

If you do it during the day, the scorching sun may affect the chlorine levels or the other pool chemicals and render them ineffective. You shouldn’t use your solar cover immediately after shocking the pool.

Wait for the chlorine concentration to go down. The high chlorine concentration might damage your solar pool cover. You can, however, use safety covers that have no heat transfer ability to protect the entire pool surfaces.


Solar covers don’t cause algae to grow – at least not directly. They may accelerate it though, by heating the water and making an existing infestation several times worse. The risk of this happening is much higher if your water already has a high phosphate level or low chlorine levels.

The good news is that you can prevent your solar blanket from breeding bacterial spores by taking the steps above.

If you have other pool-care suggestions on how to maintain an algae-free pool, please let us know in the comment section.