Has it affected the pH of the effluent? When I ran a second stage, my effluent was still 6.7 (it was 6.7 going into the second stage, it was 6.7 coming out). But I didn't think to measure the tank's pH swings as a result (mind you I didn't have a nifty little chart logger like a Profilux to make it easier to do so
).
That's awesome that you've noticed a difference already, guess there really is something to the second-stage then.
Question, what is your effluent flow rate?