Operating a CO2 System without nocturnal switchoff?
I intend to put my CO2 system into operation. However, I do not have a nocturnal switchoff unit. Is there any other way to interrupt CO2 addition at night?
Basically, there are the following ways to interrupt CO2 addition at night:
* a pH regulated solenoid valve (seramic)
* a solenoid valve triggered by a timer
* a hose clamp put on by hand
* closing the CO2 bottle in the evening, and opening it again in the morning
The last method is so impracticable that I cannot seriously recommend it. A hose clamp put on by hand can also be only a short term solution, if at all – sooner or later one will forget it, also the mechanical stress is not good for the hose. This leaves the first two methods as a permanent solution. The seramic provides better precision, the second solution is cheaper but of course, unlike the seramic, does not take the current consumption by the plants into account.
Is it necessary to interrupt the supply at all? Is there a risk of fish suffocating?
There should be no problems in case of low level CO2 addition. There is, however, indeed some risk in case of high level addition - CO2 is not taken up during the night when there is no light, and may then reach dangerous concentrations.
Summary: Although there may be possibilities to switch off the CO2 supply without an automatic switchoff function (triggering a solenoid valve via pH control or timer) I cannot recommend proceeding this way as it is impracticable.
Dr. Bodo Schnell