I have a small Red Sea 100mg/hr max. ozonizer on my 90 gallon. As far as water clarity, it's the best. It makes my water so clear and colorless that you don't know there's water in there. That's about where it ends.
I have been running ozone in my tank off and on since I set it up In 2006. I have it T'd right into my Venturi intake tube on my skimmer with no carbon on the skimmer output tube and have no problems. I don't hold much faith in its ability to oxygenate the water or to kill too many baddies though. Also, the samll ozonizers that are made for the hobby like the 100mg/hr models are perfectly safe and there is virtually no way to overdose your tank, unless you run it directly into the main display. It should always be run through the skimmer. There are other models that are more hefty like the Ozotech that goes to 450mg/hr and require more monitoring and have a much higher risk if not properly set up and titrated for the specific tank.
With that being said there are other ways to get clear water such as carbon and UV sterilizers. IMO, you will get a bigger bang for your buck with a UV sterilizer than with ozone. However, using ozone and a UV sterilizer is using the old one-two punch and IMO one can aid the other in helping to cut down on its workload. Or, if you are like me, and like gadgets then get a small ozonizer!
