I think you should look at spasolutionbc.com. Ive been using it for 5 years and it works. Look up the website, call the guy and talk to him. I do not use chemicals in my tub because of that stuff, and everything is fine. I'll never use anything else.
I have used spa solution in my tub for 5 years and it works great. I havent had chlorine or bromine in my tub, except for shocking purposes, in 5 years