If a conventional chalk reactor, the AquaCare magnesium reactor or the AquaCare carbon dioxide reactor COR (CO2 fertilizing unit) should not run all the day you can use a night shut-off. Especially at night the animals (corals) and plants / algae do not need carbon dioxide. So at this time span you do not need a CO2 supply. Many pH-controller are not able to stop the carbon dioxide feed, too. The AquaCare night shut-off can solve this problem.
The night shut-off consists of a timer and a rigid solenoid valve, that is suitable for CO2 very well. The solenoid of the unit should be mounted between carbon dioxide pressure tank and the CO2 check valve. The mains cable must be connected with the timer. If you use a compacts pH-controller the solenoid should be connected between controller and carbon dioxide pressure tank. You can program the timer in that way that the solenoid shut on only at night. With this operation mode you can safe a lot of carbon dioxide.