Sodium Bicarbonate to raise the pH, Sodium Bisulfate to lower the pH, target pH is 7.2 - 7.8, Potassium Monopersulfate as a "shock oxidizer" (this I image is not good to eat, just by the ominous name of it!), Chlorine (probably dissipates with aeration?) and minerals. I think the minerals are to help stabilize pH and to create hardness, but I don't really know, nor do I know what the specific minerals used are. Then there's an ozone injection thingy and a quite extensive mechanical filtration system.

My wife wanted the hot tub, so I said she gets to be the chemist. I just do the soaking and relaxing myself!

The water looks as clear and fresh as a remote mountain stream. However, ... !!!