Green Treat is an E.P.A. registered algicide formulated for the killing and elimination of green alage. It is patented, also.
Green algae grows all over and turns the water into a cloudy, green swamp.
When the algae is on the walls, most of it will brush off. If none will brush off, look out, you probably have metal staining. Use Pool Stain Treat for metals. A clear green pool is not green algae. That's a metal problem and you should use United's Pool Stain Treat.