Proper CA and Alk levels will keep your rocks purple, this can be achieved with regular water changes. As Chris stated, seed your tank with purple rocks. I know my CA is lower than desired when my coralline starts fading on the back glass. As Tebstan stated, I too would like to see a test, not to see it it works or not, but in comparison to just plain ol water changes with accurate CA Mg and Alk levels. Sound like just another supplement with a fancy name, and hefty price tag.