I have a heavily planted 30 gallon tank with high-pressure CO2 injection. I
don't have any shutoff valves on the co2 to control output in the evening
when the lights are out, so I run my air pump and drive a good amount of air
through my coil air stone for several hours to try and level off the co2 in
the water..

Is this a good idea, or not really recommended?

A lot of people do this. Each tank is different, of course, but if it works
for you, great.

I like to set both my aeration and surface turbulence high enough that I can
have both running all the time, without the CO2 getting too high at night or
too low during the day. Some Co2 is wasted this way, but if you have
compressed CO2, refills are fairly cheap.


Leigh

http://www.fortunecity.com/lavender/halloween/881/