I have Dr Katz ozonator, it says to run it for 20 minutes in the hot bath.
I used it differently, took a gallon of cool water (heat disipates oxygen faster), ran the ozonator on it for 30 minutes. In the meantime I prepped the hot bath and just poured the newly ozonated water in it.
Was a great bath, I included epson, baking soda and Sea Salt s too.