When you turn the aerator on, does the water coming in "splash" or churn the top of the water where it enters? If so, using this will do 2 things: cool the water, and raise the pH without affecting TA at all. The first might be desirable if you have a really hot summer, and the pool water gets warmer than you would like. The second is desirable if you want to lower the TA. It lets you add acid which lowers both pH and TA, and then raise the pH while leaving the TA alone so you can add more acid to lower both of them again. (I don't know of any way to lower TA without also lowering pH, and of course, you don't want to drive your pH too low.)