Carl, What you say is totally true. However, airation will have no appreciable effect unless the pH is brought low enough to cause the shift in ratio. I was only trying to clarify that. The 'shot of acid' method that just about everyone in the pool industy advocates will just lead to pH bouncing all over the place as you try to balance everything out. I wondered about it the first time I read it when I got my first hot tub and was learning how to care for it! It went against everything I had learned from my experience in keeping aquariums! When I first saw the PROPER way to do it on this forum I knew I found a home and advice I could trust!