Blue PRO is our professional-grade, concentrated phosphate remover. It is derived from rare earth elements. It is designed to react with phosphates on contact when poured in a swimming pool, and the reaction will make the water cloudy for about 24 hours. When the reaction is completed, the phosphates will have been crystallized and flocked out of solution. Vacuum the sediment to waste, and clean/backwash the filter for any remaining sediment.
Removing phosphates from the pool has many benefits. Read this to learn why.