Does Muriatic Acid Kill Algae In Your Pool? 

Written by Michael Dean
November 13, 2023

muriatic acid and algae

Every swimming pool owner knows that pools need constant care, but there may come a time when you end up with an algae-infested green pool despite doing everything you’ve been told. Pretty frustrating, right? The most common way to clear up algae is shocking, but have you ever wondered if muriatic acid can kill the algae in your pool?

In this article, I will go over whether or not muriatic acid can kill algae in your pool, other ways to get rid of algae, and more. You’ll be enjoying a clear and sparkling pool again in no time!

Main Takeaways

  • Muriatic acid doesn’t directly kill algae in a pool but helps by lowering pH, creating an environment where algae struggle to thrive.
  • To clear a green pool using muriatic acid, test water, wear protective gear, dilute and add the acid cautiously, and let it circulate.
  • Other ways to kill algae include using a pool brush, maintaining efficient filtration, employing chlorine shock, and covering your pool.
  • Muriatic acid also serves for cleaning pool surfaces and removing scale from equipment.

Does Muriatic Acid Kill Algae in a Pool? 

Muriatic acid is a more diluted form of hydrochloric acid. This pool chemical is commonly used to lower the pH level of your pool. Muriatic acid is not an algaecide and doesn’t kill algae on its own, but it greatly aids in clearing it from the pool. Algae grows best in alkaline environments or water with a high pH, specifically between 8.2 to 8.7. In comparison, the ideal pH for pool water should be around 7.4 to 7.6. So, by using muriatic acid to lower the pH to an appropriate range, you can help deter algae.

However, it’s essential to understand that muriatic acid alone may not completely eliminate an existing algae problem in your pool. It does prevent algae growth by creating a less favorable environment, though. You can use muriatic acid to lower your pool’s pH level, and then, once the level is balanced, use pool shock to eliminate the algae infestation.

How to Clear a Green Pool With Muriatic Acid 

If your pool water turns green, it generally means the pool water chemistry is off. As you and I both know, maintaining a pool is no piece of cake and involves constantly monitoring the water chemistry, including the pH, alkalinity, chlorine, and calcium hardness levels. Even still, you may wake up one morning to a green pool. If this happens, here’s how you can clear it with the help of muriatic acid.

Step One: Test Your Water

Before adding any chemicals to your pool, you should test your water. You cannot guess your way out of this. Test the pH and alkalinity of the pool water, which should be around 7.2 to 7.6 and 80 to 120 ppm, respectively. You should also check the chlorine levels of your pool, which should ideally be around 1 to 3 ppm.

Furthermore, you should also know how many gallons of water your pool holds to accurately calculate how much muriatic acid you should add.

Step Two: Put On Some Personal Protective Gear

Now that you know your pool’s pH is out of whack, you’ll need to add muriatic acid. But before you grab that corrosive acid, safety comes first! Wear goggles, acid-resistant gloves, and a chemical-resistant apron to avoid getting burnt by the acid. Also, wear long sleeves, pants, and closed-toe shoes.

Step Three: Dilute the Muriatic Acid

You should not add the muriatic acid directly into your pool as it is incredibly corrosive. Instead, make sure to dilute the acid in a 5-gallon bucket first. Additionally, always add the acid to the water, not vice versa. Adding water to the acid can cause a chemical reaction called “chemical bubbling.”

Follow the manufacturer’s instructions or use my pH calculator to calculate how much muriatic acid to add.

Step Four: Add the Muriatic Acid to Your Pool

As you walk around the perimeter of your pool, slowly and cautiously add the diluted muriatic acid to your pool water. Try to avoid splashes.

To be on the safe side, keep some baking soda nearby to neutralize any muriatic acid spills.

Step Five: Let the Acid Work Its Magic

Now, let the acid do its job. Meanwhile, keep the pump running so the acid can circulate around the entire pool.

Step Six: Test the Water Levels Again

After a few hours, test the pool water again. Check the pH and alkalinity of the water. Add more muriatic acid, if required, until the pH and alkalinity return to the recommended range. 

Step Six: Shock the Pool

Now that the water has a pH of 7.2 to 7.6, it’s time to shock the pool and kill the algae! If you’re unsure how much shock to add, use my pool shock calculator. After shocking, make sure to filter the water for at least 24 hours.

Step Seven: Clean the Pool and Filter

If needed, to help the process along, scrub the walls and floor of your pool to dislodge any algae that may be stuck. You should clean the filter as well, as a lot of algae will also be lodged there.

Other Ways to Kill Algae

Besides using muriatic acid and shocking the pool, are there any alternative methods for killing algae? Here’s what else you can consider.


As the name suggests, algaecides are chemicals specifically designed to kill and prevent the growth of algae. Different types of algaecides are available, such as copper-based and quaternary ammonium compounds. Follow the manufacturer’s instructions for proper dosage and application.

However, while algaecide is made specifically to kill algae, it’s not as effective as a good old chlorine shock. In fact, it is better to prevent algae growth rather than kill algae that has already been established. For best results, use an algaecide on top of adjusting the pH with muriatic acid and shocking the pool.


Maintaining the appropriate chlorine levels in your pool is crucial for preventing and combating algae growth. In addition to traditional chlorine, you can use stabilized chlorine products like dichlor or trichlor for longer-lasting effects.

Cleaning the Pool

I find that using some good, old-fashioned elbow grease is typically the best way to get rid of an algae infestation. Physically scrubbing the walls and floors of your pool can dislodge and break down algae, making it easier for chemicals like chlorine or algaecides to work effectively. Regular brushing and scrubbing should be a part of your pool maintenance routine.

Efficient Filtration

Make sure your pool’s filtration system is in good working condition and that you run the filter for an adequate amount of time each day (at least 8 hours a day). A well-maintained filter can remove debris and prevent the buildup of organic matter that can fuel algae growth, making it harder for algae to settle and multiply.

Other Uses of Muriatic Acid

Besides helping to kill algae in your pool, what are the other uses for muriatic acid?

Lowering pH

As you should know by now, muriatic acid’s main use is to lower the pool’s pH when it becomes too alkaline. High pH levels can lead to various problems, including reduced chlorine effectiveness, scaling, cloudy water, and, of course, increased risk of algae growth. Adding muriatic acid can bring the pH back to the ideal range.

Adjusting Total Alkalinity

Muriatic acid can also lower total alkalinity levels in pool water. High total alkalinity can lead to issues like pH instability and cloudiness. By carefully adding muriatic acid, you can bring total alkalinity to the desired range, usually 80 to 120 ppm.

Cleaning Surfaces

Besides lowering pH and total alkalinity levels, muriatic acid is also used to clean tiles and surfaces of the pool. It can help eliminate mineral deposits, scale, and even stains that may build up over time. Using muriatic acid to clean your pool is also called an acid wash.

Cleaning Pool Equipment

Pool equipment, such as filters, heaters, and pumps, can accumulate scale and mineral deposits over time. When this happens, muriatic acid can come to the rescue and clean and dissolve those nasty deposits.

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Frequently Asked Questions

Can you pour muriatic acid directly into your pool? 

Absolutely not! It is dangerous to do so as it can seriously damage your pool surfaces. Always dilute the acid in water before adding it to the swimming pool. Add it cautiously to avoid any mishap.

Can you use bleach to clear a green pool?

After balancing the pool’s pH, you can add bleach or liquid chlorine to shock the pool. But be mindful of the concentration. And if you are using household bleach, make sure it has no additives, like dyes or fragrances.

Reclaiming Your Crystal-Clear Pool

Algae in your swimming pool is a serious issue, but with the right approach and some muriatic acid, you can reclaim your sparkling and alluring pool. As you know by now, muriatic acid is not a direct alternative to algaecide and chlorine, but it can definitely help against your battle with algae. By helping maintain the proper pH levels, this acid helps create an environment less hospitable to algae growth.

Do you have any more questions about algae or pool chemistry? Just shoot me a message; I’m always happy to help out.

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