Swim University wrote:
Bob F.
I'm sure some would beg to differ on your comments. You are more than
welcome to do this research on your own and you will find out exactly
what an ozonator does. There is nothing wrong with having a ozonator
in your spa, although there is also nothing wrong not having one. But
I would have no reason to lie to my readers or give them false
information.

Both UV and ozone have bactericidal properties at the time of application
but do nothing thereafter to protect the water from later addition of
bacteria whereas free chlorine in the water can.