Black Algae: Overview, Prevention, and Treatment

Black Algae: Overview, Prevention, and Treatment
Photo by Etienne Girardet / Unsplash

Black algae is a common problem for pool owners, especially in warmer climates. It is a type of algae that forms on pool surfaces, often in cracks and crevices, and is known for its dark, almost black appearance. Black algae can be difficult to get rid of once it takes hold, making it important for pool owners to take preventative measures and act quickly if they suspect a problem. In this article, we will provide an overview of black algae, its causes, and the best ways to prevent and treat it.

What Causes Black Algae?

Black algae is a type of cyanobacteria that grows in warm, sunny, and humid conditions. It can be introduced into a pool by a variety of sources, including contaminated pool equipment, pool toys, or bathing suits. Once it takes hold, it can quickly spread throughout the pool and attach itself to pool surfaces, making it difficult to remove.


The best way to prevent black algae from forming in your pool is to maintain proper water chemistry and keep your pool clean. This includes:

  1. Regularly testing your pool water and adjusting chemicals as needed to maintain the correct pH and chlorine levels.
  2. Brushing the pool walls and floors regularly to prevent algae from attaching and growing.
  3. Vacuuming the pool regularly to remove any debris that can feed the algae.
  4. Keeping pool equipment clean and well-maintained, including filters and pumps.
  5. Not allowing people to enter the pool with contaminated items such as toys or bathing suits.


If you suspect black algae has taken hold in your pool, it's important to act quickly to prevent it from spreading. Treatment options include:

  1. Scrubbing the affected areas with a stiff-bristled brush to remove as much of the algae as possible.
  2. Shocking the pool with a high dose of chlorine to kill the algae.
  3. Adding an algaecide specifically designed to treat black algae.
  4. Brushing and vacuuming the pool daily to remove any remaining algae.
  5. Maintaining proper water chemistry and filtration to prevent the algae from returning.

In severe cases, it may be necessary to drain and clean the entire pool to completely remove the black algae.


Black algae is a persistent and unsightly problem for pool owners, but with the right preventative measures and treatment, it can be managed. By maintaining proper water chemistry, keeping your pool clean, and acting quickly if you suspect a problem, you can prevent black algae from taking hold and ruining your pool. If you do find yourself with a black algae problem, be sure to consult with a pool professional to determine the best course of treatment for your specific situation.