There are three types of people on this board regarding Ozone.
1. Have no clue.
2. Ones who have looked into it, understand it, and still hesitate to go for the next step because they believe it is risky as O3 is a potent poison.
3. The other minority made the plunge, including myself, and love it. There are precautions that you have to take when using O3 to make sure that it does not leach into your main display tank.
As far as HOB goes, I dont recommend it at all. You should use it in the sump in conjunction with carbon.
Just do a search for O3. There are several threads here as well as an advanced thread.
Regardless which way you go make sure you use it in conjuction with a Redox controller.
HTH,
Herman