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Green Algae in Swimming Pools: How to Identify and Treat It

Green Algae in Swimming Pools: How to Identify and Treat It

Green algae is a common type of algae that can grow in swimming pools. It appears as a green, slimy film on pool surfaces, and can cause the water to become cloudy or discolored. Green algae is generally easy to treat if caught early, and there are several steps you can take to eliminate it.

Identifying Green Algae

The first step in treating green algae is identifying it. Green algae can appear as a slimy, green film on pool surfaces, or as green water. It tends to grow in areas of the pool where there is limited circulation or in areas that receive a lot of sunlight. If left untreated, green algae can spread quickly and make the pool water unsanitary for swimming.

Treating Green Algae

The following are steps you can take to treat green algae in your pool:

  1. Brush the pool: Use a pool brush to vigorously scrub the affected areas to loosen the algae from the surface. Be sure to brush all the surfaces of the pool, including steps and corners.
  2. Shock the pool: Use a pool shock treatment that contains a high level of chlorine to kill the algae. Follow the instructions on the package carefully. Be sure to maintain the pool’s chlorine levels for several days to prevent the algae from regrowing.
  3. Add algaecide: Add an algaecide to the pool to help prevent the algae from regrowing. Follow the instructions on the package carefully.
  4. Run the filter: Allow the pool filter to run for at least 24 hours to help remove the dead algae from the pool water.
  5. Vacuum the pool: Once the algae has been eliminated, vacuum the pool thoroughly, paying close attention to the affected areas.
  6. Maintain the pool: Once the algae has been eliminated, continue to maintain the pool with proper chemical balances, regular brushing, and vacuuming to prevent the algae from returning.

Preventing Green Algae

Prevention is key to avoiding green algae growth in your pool. Here are some tips to keep your pool clean and healthy:

  1. Maintain proper chemical balance: Regularly test the pool’s pH, alkalinity, and chlorine levels to ensure that they are in their recommended range. Adjust them as necessary to keep the pool water healthy and clean.
  2. Clean and brush regularly: Regularly brush and vacuum the pool to remove dirt and debris that can promote algae growth.
  3. Ensure proper circulation: Ensure that your pool’s pump and filter system are working properly, and that water is circulating properly in all areas of the pool.
  4. Limit sunlight exposure: Algae grow best in direct sunlight, so consider planting trees or adding umbrellas to shade your pool.


Green algae can be a frustrating problem for pool owners, but with proper treatment and prevention measures, it can be eliminated and prevented from returning. Identifying green algae early and taking steps to treat it immediately is crucial to keeping your pool clean and healthy. Regular maintenance, proper chemical balance, and prevention measures can help prevent green algae from growing in the first place. By following these steps and consulting with a pool professional when necessary, you can ensure that your pool remains a safe and enjoyable place to swim for you and your family.

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