Phosphate (PO4)
Phosphate is a sub-micron solid that is utilized as a food for unwanted algae in a saltwater tank. This type of algae causes much frustration in the hobby due to its unsightly appearance. Many city water and wells contain phosphate. Public water systems (PWSs) commonly add phosphates to the drinking water as a corrosion inhibitor to prevent the leaching of lead and copper from pipes and fixtures. Inorganic phosphates (e.g., phosphoric acid, zinc phosphate, and sodium phosphate) are added to the water to create orthophosphate, which forms a protective coating of insoluble mineral scale on the inside of service lines and household plumbing.