Q:
In a freshwater plantedtank you use CO2. Now the CO2 in controlled via pH probe etc. which in turn controls a solenoid valve. This is controlled by the profilux powerbar.
Is there anyway to control it so it can be turned completely off during the night? there is no point in adding CO2 to the tank at night, since plants don't use CO2 during nighttime!?

A:
There are 2 possible ways.
a) enable "nocturnal change" for the pH-control. Enter there a change of -1 for example and a time, e.g. 19:00 to 7:00. Now you have a reduced desired value for the pH-control at night. If the normal value is 7, then you have now 6 at night, the valve will not be activated.
b) use programmable logic
program a timer, e.g. timer 1 for 19:00 until 7:00
define a prog. logic: logic 1 is timer 1 AND pH1 downwards
now assign function "logic 1" to the socket instead of "pH 1 downwards"