Alkalinity?

[waterbear]

Just to clarify:
Aerating does NOT lower alkalinity (TA). It raises pH without raising TA--and nothing else can do that.

When you lower pH, you drag TA down with it. If you raise pH with soda ash or borax TA will rise--more with ash than borax. So you aerate to raise pH.

So the process is a racheting process. Lower pH and drag TA down with it. Raise pH with aeration. Repeat until TA is where you want it.

Actually, the TA (carbonate hardness, kH) is not lowered until the CO2 is forces out of the water by airation. (Lowering the pH simply shifts the ratio of carbonic acid/bicarbonate in the buffer to the carbonic acid side.) This forcing out of the CO2 by airation reduces the total amount of the carbonic acid/bicarbonate buffer system in the water. As the CO2 is forced out of the water by airation the shift is to more bicarbonate ion hence the rise in pH and the decrease in TA. The 'accepted way' (that does not work effeciently) of pouring a 'shot' of acid into the pool with no water movement to lower TA is supposed to work in the assumption that the local area of low pH created will cause the CO2 to 'gas off' in that area since it will create a high concentration of carbonic acid (CO2 dissloved in the water) in that area.