Air stone on when lights off?

If fishes are not found near the surface gasping at just before light's/CO2 comes on, or within an hour or two after light's off,then you are prolly OK with respect to Oxygen level's.
If you just like the air stones or air driven sponge filter's, then running one at night won't hurt anything.

I just turned on the lights and they are swimming around the bottom of the tank, o I guess they are all right.
Thanks for the help.

You could get a dissolved oxygen test and check the water just before lights on to see how low it goes overnight.

When I started DIY CO2 and had a cheap needle valve, I almost gassed my fish twice. I went and bought a more expensive needle valve, I almost gassed my fish a third time. This was due to the needle valve and CO2 set up supplying a very inconsistent amount of CO2. sometimes really low, then other times really high.

I added a $10 Tetra air pump and a timer, and have not had any issues gassing them since, even when the CO2 gets out of hand. So yes, for me, it was completely worth not having to worry about my 10 rainbows, 6 cories, and 2 fancy plecos, plus the handful of amano shrimp.