Just to chime in on the CO2-control question. We had our UltraLife commercial system on with the lights for our 135-gal. Needed >2 bubbles /sec and the pH swing was about 0.4. Now, keeping it on 24 hours, the pH swing is < 0.2. The CO2 ranges from about 10-25 ppm. I guess the UltraLife reactor is pretty efficient: it takes less than 1 bubble/sec. Works for me. Jared