I seem to remember there used a portion of this site for hot tubs though I can't find it anymore. My Dad just put in a hot tub and was asking similar questions. I've seen tubs foam with Bromine and I personally have never liked it's odor. My suggestion to him was going to be chlorine. Since the tub is usually covered and indoors, I thought the chlorine level could be run lower since it shouldn't vary as much as an outdoor pool. Thought 1-3PPM more than adequate.

Am I all wet? Does chlorine off gas too much with the temps? Out side of keeping the water slightly descaling or neutral on one of the scaling indices and pH in 7.6-7.8 range, what else would you need?