It really depends on the setup. If you have a tank with high light
and fast growing plants and lots of pearling, then adding the
airstone at night could be counterproductive as it would probably
reduce O2 levels. It's common for high performance tanks to carry
120% O2 saturation during the day. Adding the airstone would bubble
away both excess CO2 and O2. In lower light slower growing tanks,
especially those with high bio-loads, the addition on a nighttime
airstone may be unavoidable. Turning off CO2 injection at night
would be the preferred course of action, if fish were still gasping
then adding an airstone as a last resort.

Cheers,
Steve H.

--
Steve H.

Yesterday is History, Tomorrow is a Mystery
But Today is a Gift...That's why we call it the Present!
"Dave M. Picklyk" wrote in message
news:TI8kb.118953$6C4.48157@pd7tw1no...
I just thought I'd toss this around the newsgroup and see what
kind of
opinions I get: What does everyone think about adding more
aeration at night
when the lights are off and plants have reversed their gas roles.
I have
seen a few of my fish dwelling towards the water surface at night.
I was
thinking about the possibility of adding a timed airstone for dark
periods.
I am concerned about fluctuating PH, but more about oxygenation
for my
larger bodied fish.

Thanx for any help you can give!

Dave.

www.picklyk.com/aquascape