MD500 I did the same thing and built my own Griggs reactor. Be happy to help you with it, I have the tap you'll need to thread the tubing for your airline nipple. You mentioned to me you used to have a reef tank, if you have an Apex that is the ideal controller. Milwaukee makes a ph controller for $130. I'd get one.
I agree with Greggzz that your bubble count is way way to low. On my 55 gallon the bps is uncountable and it takes a 30" reactor to dissolve the co2 without dealing with bubbles in the tank. Its important that the length be paired with the flow rate of your pump.