Natural Chemistry PHOSfree is formulated from lanthanum (rare earth) compounds. When added to your swimming pool skimmer, a thin coating of PHOSfree forms on the filter media. As pool water flows through the filter, phosphates are reduced to very low levels. All other phosphate products will cloud pool water! Natural Chemistry's complete phosphate program results in clear perfect water, no waterline rings, no chemicals odors, and no phosphates.