The Ultimate Guide to Effectively Removing Pool Black Algae

To remove black algae (cyanobacteria) from your pool, follow these steps:

1. Clean the Filter: Start by cleaning your pool filter, as black algae can thrive in it. If the infestation is severe, replace the filter medium or cartridge.

2. Test and Balance the Water: Check your pool's pH, alkalinity, and chlorine levels, and adjust them to the recommended range:

   • Alkalinity: 100-150 ppm
   • pH: 7.4 to 7.6
   • Chlorine: 1-3 ppm.

3. Brush the Pool: Use a stainless-steel-bristled brush to scrub the pool’s surfaces thoroughly, especially in areas with rough surfaces where black algae may anchor.

4. Scrub with Chlorine Tablets: For stubborn black algae spots, use a broken chlorine tablet to scrub the spots directly, applying chlorine to kill the bacteria while you scrub.

5. Shock the Pool: Apply four times the recommended amount of calcium hypochlorite shock to kill the black algae. Do this at dusk or night to avoid chlorine degradation by the sun.

6. Run the Pump: Run the pool pump for 24 hours to circulate the chlorine and shock through the pool.

7. Brush Again: During the 24-hour cycle, continue brushing the pool to remove dead algae.

8. Clean the Filter Again: After shocking the pool, clean the filter once more to remove any dead algae debris.

9. Repeat Shocking if Necessary: If any black algae remains, apply a double dose of shock and repeat the brushing and cleaning process.

10. Test and Balance Again: Once the black algae is gone, test and balance the pool water again.

To prevent black algae in the future:

• Wash all items (swimsuits, toys) thoroughly if used in natural bodies of water.
• Maintain proper pool chemistry (pH, alkalinity, chlorine levels).
• Regularly clean your pool and equipment, and run the pump for 8–12 hours daily.
• Shock your pool weekly and sanitize any accessories or pool toys.