5 Steps to Eliminate Black Spot Algae for Good

Test and lower phosphates Black spot algae feeds on phosphates. If your phosphate level is above 100 ppb, use a phosphate remover to cut off its food source.

Shock with high chlorine Scrubbing alone won’t kill the roots. Shock the pool to 15–20 ppm of liquid chlorine and maintain that level for 24 hours.

Keep pH in range Chlorine is ineffective above pH 7.4. Keep your pH between 7.2 and 7.4 so the shock works properly.

Brush weekly to disrupt roots The algae’s roots hide in concrete pores. Brush the walls and floor weekly to physically break them up.

Check for circulation dead spots If algae returns after treatment, you likely have a spot with poor water flow. Adjust return jets or use a robot cleaner that scrubs walls.