Ozone is a highly unstable triatomic molecule and it aid in burning up organics and disease causing microbes in the aquarium, raising PH boosting dissolved oxygen and oxidation-reduction potential (redox), and maximizing the efficiency of your protein skimmer. Modern Models of the units use a corona discharge ( electrical ) method of making ozone instead of the older models where a germicidal lamp is use. The optimal application of ozone is through your skimmer, with the ozone treated water going back to a sump for mixing, out gassing and chemical filtration before returning to the main system.