Correct phosphate levels are as important as correct pH levels and are easily controlled by using a "phosphate remover". When levels of phosphates are above 500ppB in the pool water there is a risk of algae as phosphates are food for algae. Follow these rules and check your Bionizer regularly to ensure it is operating correctly and the anodes are not worn. Do these simple steps and we promise your pool will be the source of joy it was meant to be.