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How to Remove Black Algae From a Salt Water Pool

By Chrys Lin ; Updated September 21, 2017
Black algae can make a pool appear to have dirty, black spots on the surface.

Black algae can ruin the pristine look of a pool. Black algae can form in either regular or salt water pools, and it often forms in the cracks of pool surfaces, especially in cool, shady areas. It sometimes creates a heavy, slimy layer. Although black algae doesn't have any effect on the clarity of water, it does make the pool appear to have black spots on its surface.


Brush the algae thoroughly with a stiff pool brush to “break open” the slimy layer. Failing to do this may prevent the treatment from working as chemicals won't be able to penetrate the algae as well.

Shut off the pool pump.

Pour algaecide over the black algae according to the directions on the bottle and leave it overnight.

The next day, brush away and discard all the dead algae spots.

Repeat the process if you continue to see some black algae spots.

Restart the pool pump for circulation and adjust the pool's salt levels.

Make sure you maintain proper salt water chlorination levels as it helps kill bacteria and prevent black algae from growing back.


Things You Will Need

  • Stiff pool brush
  • Algaecide specific for salt water pools


  • Maintaining good pool circulation can prevent black algae because it grows when the water has low salt content and/or when pool chemicals are unbalanced.


  • This treatment is not for vinyl-lined pools as it may damage the vinyl layer.
  • Do not swim in the pool during the black algae treatment.

About the Author


Chrys Lin has been working professionally in journalism since 2003. Her work has appeared in publications in the United States and parts of Asia. She currently resides in Texas and holds a Bachelor of Arts in print journalism.