I have my CO2 on a timer set to turn on an hour before my lights and off an hour before the end of my photoperiod. From the CO2 switching on @ 8:30 am it is not until at least 2:30pm or so until I get a ph/kh reading indicating 30ppm. My CO2 indicator color also seems to confirm that this is about how long it takes to reach good CO2 levels in my tank. It's set around 1.6 - 1.7 BPS. Faster bubble rates tend to push the saturation really high by the end of the photoperiod. I've gone beyond 50ppm a few times before having to shut it down to avoid gassing fish. Still, it seems awfully long to reach correct levels doesn't it? It's a 20G and I'm using an inline Grigg style reactor. Would I be better off speeding up the bubble rate so it comes up faster but switching the gas off intermittently during the photoperiod to keep it in the right saturation range?