This thing is a monster. In one day(I know it has been over a week since I got it. I have been too busy to dialit in), it took my Alk from 7 to 15, Calc from ~300 to 500! And, that was with the effluent valve at about 75%. I have turned it down to little more than a drip to see what it does in the next couple of days. It takes a lot of CO2 due to the chamber size. One I got past 90 bpm, I pretty much used the controller to tune it. I has stayed at pH of 6.5, so either I have a steady hand or am lucky on the needle valve. Thanks for your work Eric. I am very pleased. Now, just to get some corals in there to use up the Ca/Alk. I bet this thing could handle 500 gallons.