I take to many supps at times as it is, which is why I really enjoy doing the soaks. I do supp orally with Borax but not the reccomended amounts of 1/8t. Could not tolerate the taste. I only put a pinch per quart so that I get trace amounts all day every day instead of a whopper all at once as if I were to take a capsule. This works wells for me anyway. I am sure I get much more in me, in the tub.
I suppose soaking in a flouride rich water would be a problem. I don't have that concern out here so far. But if I did I think I would still soak in Borax any way. Knowing me I would bump up the amount I used.
Don't suppose you could put a filter on to help with that?
I refuse to give up my epom salt and borax bath.