We have a small hot tub (4 person max) so I use a small ozonator (the ASO 250 from our website). I have a commercial self-drying air dryer in front of the ozonator and the ozone is introduced into the tub by the installation of a mazzei injector across the pump inlet/outlet. The water flowing through the injector creates a vacuum which draws the air through the air dryer, ozonator and balance barometer (device to measure the vacuum draw and prevent water from entering the ozonator) into the pump where it is mixed well with the water. The system runs automatically 24/7/365 and provides enough ozone to keep the water free of contaminants and crystal clear with a little extra for therapeutic benefit.When you open the cover you definitely smell ozone. In times of high use of the tub, the ozonator will not keep up so I add a little 35% H2O2 (Hydrogen-Peroxid) and use H2O2 (Hydrogen-Peroxid) test strips to monitor the water. The ozonator keeps up with the daily use of the tub by my wife and I, but when the kids come home the H2O2 (Hydrogen-Peroxid) comes out and gets added. The kids are in the tub all the time when they're home.
The only thing you have to worry about is that eventually the ozone will take out the seals on the pump. When it comes time to replace the seal, replace it with one made of viton and there will be no more worries.
Hope this helps