You have 2 other choices - chlorine and bromine; both have pros and cons. Both are easy and you don't need ozone.
Coming from Baqua, BOTH will be less expensive.
Chlorine (which is either dichlor or lithium - don't use anything else) is added before or after using the tub (most here use it after) to get a reading of 3 PPM 20 minutes after adding it. The chlorine will dissipate after a while (15 to 24 hours) and you add more either the next time you soak or every other day if you didn't soak.
Bromine is added with a feeder if your tub doesn't have a feeder in the filter area and the idea is to keep a residual (I think 5 PPM) all the time.
With both systems you need to shock once a week either with chlorine or something called MPS (first initials for a chemical compound).
You will need to clean the filters REALLY well as Baqua reacts to both from what I've read.