Phosphate Plus 4 in 1 is a revolutionary, patented formulation that removes phosphates (algae nutrients) from your pool water. Made from a natural mineral composition, this product can also be used in fish ponds and salt or fresh water aquariums. Our 1-quart bottle is easy to use. Simply add it through the skimmer while the pump is running. This is a great product to use at the open or close of swim season. Keep your pool water crystal clear and algae free with Phosphate Plus 4 in 1!