[essabee]

I do have large aquariums (200G +) with CO2 and I do pay attention to CO2 distribution. The trick is not multiple diffusers but distribution of the CO2 carrying water. Be it one reactor or several; see to it that the CO2 laden water is evenly spread throughout the length of the tank and the movement of water is from one long-side to the other (mine use upwards all along the back to downwards all along the front flow). This will give you the best distribution of CO2.