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Do Pool Covers Cause Algae? Here’s the Answer

Swimming pool covers are some of the most popular methods of warming a pool. They provide excellent comfort, but some people have noticed algae growing beneath the surface.

Is it possible that the solar cover causes more harm than good? After all, solar covers provide the warmth algae needs to grow.

Solar covers don’t cause algae because they prevent debris and rain from getting into the water. However, an algae bloom can grow quickly under a cover if the excess debris isn’t removed. Pool covers are used to warm the water and keep debris out, but they’re not resistant to algae blooms.

In this article, I’ll explain why your pool cover prevents algae and how it could work against you.

I’ll also explain why algae forms on your solar cover and walk you through how you can remove it. Let’s get started!

Does a Pool Cover Increase Algae?

A pool cover doesn’t increase algae blooms unless there’s debris under the cover, the water chemistry is unbalanced, or there’s already algae growing.

The cover provides warmth and protection for the algae, which could spread the bloom and make it much more difficult to remove.

Here’s why a pool cover can increase the algae in the pool:

  • Algae blooms need warm water, which is exactly what a solar cover provides. Your solar cover can increase the water’s temperature by up to 20 degrees Fahrenheit. Algae thrives in warm water, making your swimming pool the perfect environment if you don’t have well-maintained water.
  • Pool covers can get dirty if they’re not cleaned or stored properly. These covers catch a ton of debris, and all of it falls into the water if you don’t remove the cover properly. Furthermore, improper long-term storage will coat the cover in dirt that can enter the pool.
  • A misaligned pool cover doesn’t prevent rain and other debris from entering the water. Make sure the pool cover is a couple of inches longer than the swimming pool on all sides. Any gaps around the edges will let debris into the water, which increases the chances of dealing with algae growth.
  • Flakey solar covers cause algae blooms by dropping debris into the pool. We suggest spraying off your solar cover once every couple of weeks to prevent the chlorine from deteriorating the solar cover. This recommendation will make your pool cover last several years longer.
  • Using a pool cover for too long doesn’t let the water ‘breathe,’ which can ruin the water’s chemistry. Although the debris protection is great for the water, it needs a few hours to off-gas. The chlorine and other chemicals can settle and scorch the cover, ruining its protection.

Pool covers don’t cause algae blooms if they’re well-maintained. Using the proper chemicals for your pool will prevent the cover from inviting algae and bacteria into the water.

Remember to open the solar cover for a couple of hours each week to let the chemicals burn off and stay balanced.

Do Pool Covers Prevent Algae?

Pool covers usually prevent algae because they stop rain and debris from entering the pool. These covers also prevent evaporation, which protects the chlorine, algaecide, and other chemicals in the water.

Furthermore, a solar cover can stop various bugs from laying eggs and spreading bacteria.

So, how can pool covers prevent algae?

  • Solar covers stop debris and rain from getting into the pool. Think of all of the pollen, leaves, hair, twigs, and other debris that falls into your pool! Most of it will fall onto the cover, preventing the phosphates (algae’s primary food source) from getting into the water.
  • The cover prevents long-term evaporation, which stops the chlorine from burning out of the water. Your pool’s chlorine will last several days longer than if you didn’t have a solar cover protecting it. Combine the solar cover with cyanuric acid (pool conditioner) to get the most out of the pool’s chlorine.
  • A pool cover prevents pH and alkalinity imbalances. Rain and other debris drastically alter your pool’s pH and alkalinity. Since pool chemicals work best with balanced pH and alkalinity, it’s important to use a solar cover to prevent these imbalances.
  • You won’t have to fill the pool as much, which means you won’t have to adjust the chemicals as often. Garden hoses contain plenty of phosphates and water with an unpredictable pH. Your goal should be to add water to the pool as least as possible since you don’t want to dilute the algaecide and chlorine.

If you’re looking for a high-quality pool cover, try the Sun2Solar Pool Cover. This 12 ml pool cover comes in multiple shapes and sizes. It prevents evaporation and chemical imbalances, and it warms the water. These solar blankets are compatible with pool cover reels, so you can keep your current setup.

Sun2Solar Solar Pool Cover

Why Is There Algae on My Pool Cover?

There’s algae on your pool cover because you don’t have enough chlorine in the water, your pool’s cyanuric acid levels are too low, or you haven’t used any algaecide. Most solar covers aren’t algae-resistant, which means they have to be cleaned and sanitized if algae grows on them.

If you notice algae on your pool cover, make sure your pump is circulating water. A locked or clogged pump that can’t move the water will drastically increase the chances of algae blooms.

Follow the steps below to get rid of the algae:

  1. Remove the solar cover and spray it with a garden hose.
  2. Wipe the cover with a towel, then place it back on the pool.
  3. Test and balance your pool’s chemistry to keep the chlorine, cyanuric acid, pH, alkalinity, and hardness in check.

When used properly, pool covers are the first line of defense against algae blooms. They have everything you need for a healthy, comfortable pool.

However, they have to be maintained like every other piece of equipment for your swimming pool. Failure to do so will turn the pool cover against your pool and harbor algae.


  • Jonah Ryan

    Jonah has worked for several years in the swimming pool industry installing and repairing equipment, treating pools with chemicals, and fixing damaged liners. He also has plumbing and electrical experience with air conditioning, ceiling fans, boilers, and more. When he's not writing for Temperature Master, he's usually writing for his own websites, and

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