Steve and Mike did you modify your procals for a pH probe? I have a smaller geo which likely wont be enough once my frags grow out. Im very happy with the geo but have heard lots of good things about the procal. The lack of a ph probe port concerns me a little.
just in case your wondering, when people generally speak of the best this is unanimously the winner :
http://www.aquariumplants.com/CarbonDoser_Electronic_Co2_Regulator_p/co2.htm
Agree 100%!
I hope I get this correct, going from memory (which is not that great). Some use the ph monitor to measure the effluent and will turn on and off the Co2 Regulator accordingly. So set a control to 6.5Dkh and if it goes lower then turn off the co2. This accommodates for the regulators not being precise in it's dosage of co2 to the reactor. Thus, you can't overdose and raise your tanks Alk really high really fast. Instead, you can monitor your tanks, ph, to ensure your not dosing to much to prevent the same. But in this case, since your monitoring the tank, your one step closer to preventing issues. In the prior you don't know what is really happening to the water quality in the tank, only in the reactor.
I hope I got this right, I'm no expert on this and I don't even have one set up yet, it's just my interpretation of others comments around the web.