Ozone - Chlorine – Bromine, they are all used to sanitize the spa.  Ozone is the only one that does not contribute to the TDS accumulation.  I will not suggest or recommend the virtues of one over the other, but chlorine and bromine both contribute and accumulate in the TDS.  They alone, however do not make a "chemical soup".  You have to stir in some pH adjusters along with alkalinity increaser, some stain and scale, more chlorine, and or bromine, accompanied by some anti-foam, water clarifier, and the list can go on.  Add to this, some perspiration, body waste materials, dead skin, shampoo and hair and Cover it to simmer at 102°.  This is what I would call a “chemical stew†and a good reason for us to change our water 3 to 4 times a year, if not more often, as needed.
On the other hand, some of us may not be all too familiar with such a “chemical stewâ€.  While we still may use chlorine or bromine, some of us regularly, some of us occasionally, but nevertheless, as needed, accompanied by ozone.  Ozone does a terrific job of keeping clean water and not needing a lot of those “unnecessary†chemicals that blend together to create a “chemical stewâ€.
On service, I have seen a lot of bad water that would qualify as “chemical stewâ€.  People seem to think it’s normal, but it would gag others.  The first thing I check is the Ozonator and sure enough, it’s dead.  We put a new ozonator on, change the filter, add new water and the customer continues to be amazed with water clarity a month later.
The point is, we don’t need to contend with “chemical soup†or “chemical stewâ€, but more often than not, IF you have “chemical stewâ€, you don’t have ozone, or one that works.