I haven't got arround to setting up mine yet, but I've been reading about the optimal flow rate. What I've heard is that for the water flow rate you should use 13GPH. I'm not sure how this looks stream wise, but I was thinking of using a small 1G container to adjust the rate so that it fills in 1/13 of an hour (about 4-5 min).
for CO2 flow the guys at aquatek told me to use beween 1 bubble/sec to 1 bubble/2sec. Your PH of your effluent should be arround 6.5-6.6. If you increase your co2 then you would get lower PH and more Ca, but your PH in the tank migh also drop. Best thing is to start with the default setup of 13GPH & 1 bubble/2 sec and monitor your PH in your main tank. If it looks stable you can increase your CO2 rate or yout flow rate or both and keep monitoring the tanks PH.
72G bowfront reef
175G bowfront cichlid tank