UV is very efficient in terms of what it can do for your tank. Sure it might require a bit more power and annual bulb replacement but the results of a properly setup quality UV sterilizer speak for themselves. Aside from water clarity improvements, elimination of bacterial blooms, reduction of parasites, reduction of waterborn algae, the improvements to water quality might surprise some.. In fact, it's every bit as effective as o3 and in a shorter amount of time too. Remember, both UV sterilization and ozone oxidize organics and sterilzer the water they come in contact with. Ozone requires much less flow than a quality UV and takes longer to have a similar impact.
Many run ozone through a skimmer which is a VERY inefficient way of using ozone. You don't get ideal contact time and you end up with excess ozone in the water and the air. It's hard to funnel all that skimmer water through carbon without impacting the skimmers performance and without some residual ozone escaping through the air. Then you have the skimmers lid which also is a point that needs attention (carbon filtering) to prevent ozone from escaping into the air. There are lots of things around our aquariums that are not ozone safe and the long term effects of residual ozone can be damaging to our devices, plumbing etc. An ozone reactor with a second reactor filled with carbon eliminates those issues and allows for much more efficient and effective use of the ozone. You can control the flow through the reactor and maximize contact time. Measuring the ORP coming out of the reactor and comparing it to the tank ORP really lets you fine tune it. With a skimmer, you only control is the ozone rate.
Then you have the maintenance of the air driers or the expense of the electronic driers. If you want to do ozone right and use an ozone reactor, that adds expense as does the generator, drier, carbon etc. By the time you are done, a quality UV such as those from AquaUV are around the same cost and as I said above, they can be every bit as effective when properly sized and setup.
Earlier this year, I noticed my ORP had dropped substantially in a really short amount of time. After investigateion, I realized my UV bulbs in the AquaUV 114 watt sterilzer had died. Normally I replace them every year but I had gone just over 1.5 years without replacing them. I ordered up new bulbs and in a weeks time, ORP went from 275 back up to 400. I ran ozone for years and never saw those kinds of improvements in such a short amount of time.
This is my ORP graph showing the ORP increase over the course of 6 days immediately after changing the bulbs. You won't get these kinds of results with ozone alone.
