George I have a Precision Marine Unit. I will take some pics of it for you. The co2 enters I believe at the bottom where the pump sucks it through. Then it passes through the media. It is keeping my tank Ca. at about 450 PPM. I use salifert to test. Single Chamber. The effluent water comes out on the top of the unit. The rate is about 75ml. a minute. PH is about 6.5ish.

HTH