Solenoid and stable level of CO2?

[Sf1]

Hi,

When my solenoid block the CO2 at night, after some hours the drop checker become blue.

So it's mean that my co2 level is not stable? Or this is normal situation and won't promote algae?

My lighting schedule 2pm to 9pm.
My co2 schedule from 7am to 9pm.

When the light on, the drop checker is green.

Thanks for advice.

 

[Old Scales]

This is what you want. When the lights are off you want the CO2 to stop also. This lets the CO2 dissipate. If you kept the CO2 running with the plants not using it you waste CO2 and risk gassing your fish. You want the CO2 to start about an hour before the lights come on and off an hour before the lights go off. OS.

 

[aqua_chem]

As mentioned, CO2 is volatile and will rapidly leave the tank after it gets turned off. The stability issues should only come into play when the lights are on.