Algaecide

Chemicals that inhibit, prevent, or control algae. Some work as wetting agents (polymers and quats), allowing chlorine (or another sanitizer) to penetrate the shell of the spore. Some cause the algae to expand (and stop reproduction) so it may be filtered out. A few types work by concentrating the chlorine intensely, causing the water to "smoke and froth". Some control algae by preventing it from photosynthesis processes! Copper, Silver, and Zinc are used in a myrid of methods, from liquids to mineral beds impregnated with them. Silver actually kills algae outright, but it leaves a "residual killing action of the walls and floors", a nice way of saying slight staining. Of course, all sanitizers are algaecide, but occasionally they need help.