CO2 and solenoids

I didn't say that solenoids were essential, I said that I would
recommend them, and here is why: I like the idea that no CO2 is going
into the tank at night. I have a Sandpoint CO2 reactor, and one night I
accidentally left the CO2 on all night. (I plugged the solenoid into a
different outlet. One without a timer hooked to it.) When I returned the
next morning, my Angels were gasping at the surface. The CO2 may have
been flowing too fast anyway, but I would eventually have caught this
with a PH & KH test. The Angels made it, but it was close. Also, does
photosynthesis immediately leap into high gear, or does it take the
plants a while to realize that the lights are on? For me, it's one less
thing to worry about when the lights are out.

To an earlier questioner, some signs of too much CO2 for your fish. A
general lethargy or listlessness at first and gasping at the surface
later. As you might think, Gouramis seem to be fairly tolerant of
excessive CO2 given their ability to breathe air.