Black spots between the leakages of tiles  

• Symptoms:  Formation of brown or black algae spots on pool wall or on pool bottom.
• Cause: growth of an algae called Phormidium inundatum very resilient and tenacious
• Recommendations: adjust pH and add 3 Kg of granular chlorine per 100 cubic meters in the tank (for plant operating and paying in small doses chlorine in the skimmer). Hold for three or four days these conditions of high chlorine tank and until the until algae not detach easily with the broom. Under these conditions avoid wet.