Ozone is used to kill harmful bacteria and pathogens as well as making the water crystal clear. It interacts with dissolved organics to form a complex that is more easily removed by a protein skimmer resulting in clearer water than running carbon alone. This allows more light to penetrate the water for corals and can assist in their  coloration and overall health.  Many manufacturers recommend 0.3 to 0.5 mg/hour per gallon of aquarium water but many aquarists use less, or do not use it all of the time, only to clear the water when needed. The addition of an air dryer can make your ozone unit run much more efficiently as ozone breaks down rapidly when exposed to humidity.