I never wait for my chlorine level to drop before adding the metal out. Metal out will use up chlorine, but I always keep my levels up so that I don't get an algae bloom, because then you are in a loop - algae bloom, shock then get stains, get rid of stains with low chlorine, and go around again I just keep up with the pool by adding sequestering agent and keeping the water balanced. Once you get the water cleared, and the water balanced I will help you with the stains. Remember the most important thing is to have a sanitized balanced pool. You can swim in a pool that has stains, but not in one that is not sanitized.