Tim has brought to my attention that using a solenoid and timer to shut off the CO2 during the night when the lights go out will create a large Ph shift.Ive read that this is the better approach since plants dont utilize CO2 in darkness.In Aquarium Plant Paradise by Takashi Amano page 37 he states"Turning off the sytem at night prevents unnecessary lossses of CO2 and undesireable drops in Ph value". Florida driftwood shows a schematic for setting up a solenoid to use in conjunction with a timer or controller.What do you think is the proper setup.