Depends on the tank. Diffusers look cool there easy to hookup. I feel diffusers are good for small tanks by themselfs. If using one on a bigger longer tank you need supplemental water circulation to get the co2 dispersed around the tank better. Reactors powered with a some sort of water pump has more pressure behind it to disperse it better around the tank. I myself like to inject my c02 through the water pump so the pumps impeller mixes the co2 then into the tank through a spraybar that is submerged under the water surface.
