How to Get Rid of Black Algae in Pool

By Algal Web

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Having a sparkling clean and inviting swimming pool is the dream of every pool owner. However, the presence of black algae can quickly turn that dream into a nightmare.

Black algae, scientifically known as Blackspot Algae or Nostoc, is a persistent and stubborn type of algae that can infest your pool, leaving unsightly black or dark green spots on the surfaces. 

In this article, we will explore effective methods to get rid of black algae and restore your pool’s pristine condition. It’s crucial to address this issue promptly to prevent further growth and potential damage to your pool.

Understanding Black Algae

Black algae are a particularly challenging form of pool algae due to their tenacious nature. They have a layered structure that allows them to embed themselves into porous pool surfaces such as plaster, concrete, and even vinyl liners. 

The dark coloration is due to the presence of a protective layer, making it difficult for regular pool chemicals to eliminate them. Black algae typically thrive in warm and sunny conditions, which is why they are more prevalent during the summer months.

The primary factors contributing to black algae growth in pools include poor water circulation, insufficient filtration, inadequate pool maintenance, and unbalanced water chemistry.

Neglecting these aspects can create an environment conducive to algae growth, allowing black algae to take hold and flourish. If left untreated, black algae can not only ruin the aesthetic appeal of your pool but also pose a health risk to swimmers.

Preparing for Treatment

Before diving into the treatment process, it’s essential to take necessary precautions and gather the required tools and equipment. Begin by wearing protective gear such as gloves and goggles to safeguard yourself during the cleaning process. 

You will need a stiff-bristle pool brush, a telescopic pole, a vacuum system, and a suitable black algae treatment product. Additionally, it’s crucial to ensure that your pool’s water chemistry is properly balanced and the filtration system is functioning optimally.

Step-by-Step Guide to Removing Black Algae

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Step 1: Identifying the Affected Areas

Carefully inspect your pool to identify the areas affected by black algae. Look for dark spots on the pool walls, floors, and even in hard-to-reach areas such as corners, cracks, and crevices.

Black algae often thrive in areas with poor circulation, so pay special attention to these regions.

Step 2: Brushing the Affected Surfaces Vigorously

Using the stiff-bristle brush attached to the telescopic pole, vigorously brush the affected surfaces to break the protective layer of the black algae.

Apply firm pressure and focus on each spot for a thorough cleaning. It’s important to note that brushing alone may not eliminate black algae, but it is a crucial step in the treatment process.

Step 3: Applying an Effective Black Algae Treatment Product

Choose a reliable black algae treatment product from your local pool store or consult a professional for recommendations. Follow the product instructions carefully and apply the treatment directly to the affected areas.

Some products may require pre-dissolving before application, so ensure that you mix them according to the manufacturer’s guidelines. Apply the treatment generously, ensuring that it covers the entire affected area.

Step 4: Allowing the Treatment to Work and Monitoring Progress

After applying the treatment, allow it to work as per the product instructions. The treatment will penetrate the algae and gradually eliminate it. Regularly monitor the progress to ensure the treatment is effectively breaking down the black algae.

Keep in mind that black algae can be stubborn, and it may take several days or even weeks to see significant improvement.

Step 5: Repeating the Treatment if Necessary

In cases of severe black algae infestations, it may be necessary to repeat the treatment process. Follow the product instructions and reapply the treatment as recommended.

Persistence and patience are crucial when dealing with black algae. Monitor the progress after each treatment and evaluate if additional applications are required.

Step 6: Vacuuming and Clean the Pool Thoroughly

Once the black algae have been eliminated, it’s time to remove the debris from your pool. Use a pool vacuum to thoroughly clean the pool, paying extra attention to areas previously affected by black algae.

Empty the vacuum bag or clean the filter regularly to ensure optimal suction and efficiency. Additionally, clean or backwash the filter to remove any residual algae or debris.

Step 7: Regular Maintenance and Prevention Strategies

To prevent future black algae growth, establish a regular pool maintenance routine. This includes testing and balancing the water chemistry, maintaining proper filtration and circulation, brushing the pool surfaces regularly, and using appropriate algaecides and shock treatments.

By staying proactive with your pool maintenance, you can significantly reduce the chances of black algae reappearing.

Prevention Techniques

Preventing black algae growth is more manageable than dealing with a full-blown infestation. Here are some preventive measures to incorporate into your pool maintenance routine:

  • Regular pool maintenance: Perform routine water testing and chemical adjustments to maintain proper water balance. Regularly skim the pool’s surface and clean out the skimmer baskets to remove debris.
  • Brushing and cleaning: Regularly brush the pool walls, floors, and other surfaces to prevent algae from taking hold. Pay attention to areas prone to stagnant water or poor circulation. Additionally, consider using a specialized pool brush specifically designed for black algae removal.
  • Shock treatments and algaecides: Regularly shock your pool with appropriate chemicals to kill any potential algae spores. Shock treatments raise the chlorine levels in the pool temporarily, effectively eliminating any microorganisms. Additionally, use algaecides as a preventive measure, especially during the summer months when algae growth is more common.
  • Filtration and circulation: Ensure that your pool’s filtration system is in good working condition. Clean or backwash the filter regularly to maintain optimal performance. Proper circulation helps prevent stagnant water and algae formation. Consider running the pool pump for an adequate duration each day to ensure proper water circulation.
  • Sunlight exposure: Black algae thrive in sunny conditions. Consider using a pool cover when the pool is not in use to minimize sunlight exposure and reduce the chances of algae growth.

Seeking Professional Help

In cases of severe black algae infestations or if you find it challenging to eliminate the algae on your own, it is advisable to seek professional assistance. Professional pool maintenance services have the expertise and specialized equipment to tackle stubborn black algae effectively.

They can conduct a thorough assessment of your pool, provide targeted treatments, and offer ongoing maintenance advice to prevent future infestations.


Black algae can be a persistent nuisance for pool owners, but with the right approach, it can be eliminated, and your pool can be restored to its former glory.

By following the step-by-step guide outlined in this article, practicing preventive measures, and seeking professional help when needed, you can ensure a clean and enjoyable swimming experience for yourself and your guests. 

Remember, regular maintenance, proper water chemistry, and proactive cleaning are the keys to keeping black algae at bay and maintaining a beautiful and healthy pool. Invest time and effort into your pool’s upkeep, and you’ll be rewarded with a pool that you can enjoy all season long.

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