If I under stand this right: I think of the co2 like water filling a cup. The cup has three levels the first one is the fill , the second the ideal level, and the third to much. So we want this to stay at the second level for the total of the photo period. I think of the co2 as a drip filling the cup, the slower the drip the longer it will stay at the desired level with out over flowing. But the longer it will take to get to the desired level. This may mean that the timer should be turned on a few hours before the lights come on. At that slow rate it should stay at the green state for the whole photo period with out over flowing and going in to the third level. So with two adjustments we can time the bubble rate for the duration of the photo period and the timer so it is filled to optimum level when the photo period begins. Taken in to concern with the bubble rate is the pants up take so the cup dose not fall in to the fill level. This is what I use to visualize CO2. Is this one par with what is going on?