A year ago I was taking some water treatment professional education classes on, among other things, methods of disinfecting water. This particular class compared things like chlorine, chloramine, ozone, and UV. Among the water quality experts UV was by far the preferred method of disinfection particularly because it does not leave a residual and therefore makes for healthier water to consume. However, the regulating powers that be still require a Cl residual for tap water production partly because they don't understand the chemistry and partly because the code is just out dated. Ozone was mentioned as a better alternative to Cl for a number of reasons (some I don't remember & some not relevant to aquariums) but particularly because it had a measurable residual good for reporting reasons only. In a nutshell, as far as disinfection goes, there isn't anything ozone can do that UV can't do better- more or less.
They talked about redox / ORP a bit too and I wish I could remember more on that but the one lasting impression I had was that ORP as it applies in the aquarium hobby community is vastly misunderstood. I got the impression controlling ORP with ozone in an aquarium is letting the tail wag the dog. We (marine aquarists included) should be focusing on other more conventional aspects of water quality and ORP would take care of itself.
