Do Solar Pool Covers cause Algae? FIND OUT!

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It’s no news that pool covers assist in keeping leaves and debris out of pools at home or at public places. Thereby beating down on the cost of general swimming pool maintenance.

A solar pool cover lets you enjoy this benefit and plenty more – For starters, it helps with pool heating, warmth, and evaporation reduction.

Besides providing these purposes, there is a trending question – do solar pool covers cause algae?

Solar blankets can start to get an algae build-up just like other pool accessories if you don’t keep them clean.

To clean algae off your solar blanket, try this: I think I’d find a convenient time when no one will be using the pool for a day or so, raise the Cl to shock and pull the cover over the pool, maybe even submerge it to get the pool water over it all and maybe even brush it with the pool brush.

I’d expect to have to do some clean-up after but if it’s otherwise clean, I think most of the algae would filter out.

Does Leaving A Pool Cover on Cause Algae?

Leaving a pool cover on your pool does not make the pool go green (have algae). But, since solar covers warm water, they might accelerate algae growth if your water already has algae/algae pores.

Does A Solar Cover Cause Algae?

No! Solar covers do not cause algae growth. Instead, the best solar pool cover warms your pool water while still protecting it against UV rays and pool dirt.

Never has it encouraged or caused algae growth directly. But, if your pool already had algae on it or if your pool water contains algae spores, the water warming could increase their progression, especially if there are phosphates in the water.

If that is the case, then there are steps you can take to prevent algae from present in your water.

This post will take you through some of these preventive measures.

How Does A Solar Pool Cover Contribute to Algae Growth?

All solar covers are primarily made to serve as a solar energy transfer blanket for letting in energy from the sun pass through it, trapping it inside the pool.

The goal of a solar pool cover is to heat the pool water while still protecting the heat from getting lost. The water surface covering also aids in the prevention of water evaporation while also keeping the leaves and debris out.

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Algae growth typically occurs when:

  • The bacteria get 10-15 hours of sunlight per day
  • If the water temperature stays anywhere between 60-80° Fahrenheit.

So, while a solar pool cover won’t cause algae in your swimming pool. It can warm the water by 8 degrees on a typical hot day. In other words, your solar pool cover could rapidly accelerate the algae.

In a matter of 8 hours, you could be dealing with a full-grown algae attack.

The attack could come in earlier if your pool chlorine levels are low, phosphate is present in the water, and water pH is high.

  • Phosphate is a happy 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 provides you with tips on what to do to prevent algae growth when you’re using a solar pool cover and how to wash algae off a solar pool cover.

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

Here are some actions to take to prevent an algae outbreak from occurring in your pool:

  • Understand Your Pool and Use the Right Solar Cover

Solar could be boosting the algae growth in your pool by letting sunlight pass through to the pool water and alter the chlorine levels in the process.

Facing an algae problem could also be from the fact that you’re living in an area with temperatures favoring their growth, and the sun is only acting as a growth booster.

The best cover we would recommend for you would be a bubbled solar blanket with a clear top and Dark on the bottom. The clear top lets energy shine through while the dark bottom absorbs heat and transfers it.

It’s an amazing piece of technology that retains heat well.

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

  • Clean the Cover Before Use

Always clean your solar cover using a cover cleaner before and after use. The cleaner eliminates any leaves and spores, leaving your solar pool cover clean.

We don’t recommend using bleach used to clean laundry or floors before laying it on your pool, as that could void the warranty or deteriorate your pool cover.

However, make sure the ppm of the chlorine in the bleach is less than three, or it could damage your pool cover, real bad.

  • Never encourage Stagnant water, Keep the Water Moving

Stagnant water is a breeding ground for algae. They multiply quickly 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!

Yes, it is safe to run a pool pump when your solar pool cover is on. You can run the pump as often as you can to keep the water moving.

A variable-speed pump lets the constant water flow without high energy usage.

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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, before and after Use

As humans, we might forget and leave our solar pool cover on as a protective pool cover for far too long that it beings to collect lots of debris – this is bad.

Why? Because the debris and leaves could become too heavy for the solar cover and begin ripping it or even cause it to sink in your pool. That leaves your to pool exposed and you risk the chance of letting algae pores into your pool.

The dirt, pollen, and debris 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.

So, what do we recommend?

Keep your solar cover clean and free of leaves and debris.

If you’re planning not to use the swimming for more than a week, the best action would be to close it with a pool safety cover.

  • Keep the water chemistry balanced

Imbalanced pool chemistry gives room for algae to grow, very quickly.

A minimal drop in chlorine leaves could turn your swimming pool into a partying ground for the green algae.

Other factors that affect your pool chemistry include:

  • Bugs
  • Vegetation
  • Rainwater
  • Run-off water,
  • And any other contaminant that could easily find its way into the swimming pool

You should frequently test your pool water from time to time.

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:

Chlorine 1-3 ppm
pH 7.2 – 7.6
Calcium 200 ppm
Alkalinity 80-100 ppm
Cyanuric Acid 30-50 ppm

Getting anything below these levels means you need to initiate a balance 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.

Do Solar Pool Covers cause Algae

  • Shock Your Pool Regularly

Pool shock remains one of the most effective means of killing pool algae.

It’s mainly applicable when you notice there are algae in your pool.

You could also take certain measures to protect your pool against the algae spores that might have found a means of introducing themselves to the 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 spread 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.

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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.

  • Keep an eye on the Pool Regularly

Yes, keep an eye on your pool during the summer and winter months. Algae notoriously attack pools during summer because of the warm temperatures.

If you notice some brown or yellow stains around the pool stairs, green mucky around the dark corner, or black sand-like stuff on the pool floors, there could be an algae outbreak in your pool.

The best course of action at this point would be to shock your pool and add algaecide after 24 hours.

  • Use Algae Starver

An algae starver gets rid of phosphate build-up in the pool water, which serves as algae food, thereby starving it.

Once the chemical has been added, 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 is no food, the algae die.

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How To Clean Algae Off Solar Cover

  • Hose it off well
  • Then use a pump sprayer to spray it down with a shock level mixture of bleach and water.
  • Rinse off the cover and then you can put it on the pool to slow down some of the FC use,
  • Lastly, let it dry in the sun and roll it back up.

Should I Remove Solar Cover During the Day?

During summer? No! This is the time when the solar pool cover heats the water by allowing the sunlight into the swimming pool and blocking it inside. But, if you live in an area that gets scorching heat during the day and extreme cold during the night, then you might remove it during the day.

Does a Pool Heat Up Faster with The Solar Cover On?

Of course, YES. 9 out of 10 pool owners confirm that their pool gets warmer faster after installing and using a solar cover by trapping the warmth of the sun.

That can even save you on heating bills, and you can use the electricity for something else.

Can You Cut a Solar Pool Cover to Size?

Yes, 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. But, remember, solar covers are soft, and it’s easy to cut too much.


Do solar pool cover cause algae? No, they don’t. In fact, solar pool cover warms your pool, keeps the pool water warm, and protects against evaporation, and more, but not encouraging the growth of algae.

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 keep it clean before and after use, regularly shock the pool, and discuss the rest.


Author: Howard S. Baldwin

My name is Howard S. Baldwin. I am a work-at-home dad to three lovely girls, Jane + Hannah + Beauty. I have been blogging for the last 3 years. I worked for other Home and Lifetsyle blogs, did hundreds of product reviews and buyers’ guides. Prior to that, I was a staff accountant at a big accounting firm. Needless to say, researching and numbers are my passion. My goal is to be an informative source for any topic that relates to DIY life and homemaking.

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