Its active ingredients naturally bind phosphates, rendering them ineffective as a food source for algae. Reduce 3,000 ppb add 32 oz./10,000 gallons. Phosphates– a key nutrient to algae, phosphates can significantly accelerate algae growth. Introduction of phosphates come from several sources; municipal water suppliers, fertilizers, detergents, bather/bird waste and some mineral treatment products. Treat ppb when test is 1,000 or above.