The present invention provides a composition for treating recirculating or stagnant water. The composition contains a phosphorus-containing compound, which is metaphosphate compound, a polyphosphoric acid or a polyphosphate, and one or more zinc compounds. The phosphorus-containing compound is a compound which is not readily hydrolyzable to an orthophosphate. In another aspect of the present invention, provided is a method of controlling algae in a body of recirculating or stagnant water using the composition.
