Overnight Aeration

[SCMurphy]

Bob,
Yes there are some plants that can absorb CO2 in the dark,. They use a different pathway which I could explain but not many people would want to read that. The plants do this in environments that have limited CO2 levels to out compete other plants. However, it is like you said, running the air pump overnight should not be a problem.

[Sonny Disposition]

How long does it take to suffocate a dozen shiners in an unaerated bait bucket?
(That's a rhetorical question, I'm not expecting an answer.)

With the lights off, and without aeration, I would think CO2 levels would build up fairly rapidly-- especially if you cut back on circulation/filtration.

[JLW]

I will tell you all this, since I've been doing it, I have had almost no losses. A few the day or so after ... but then whatever the problem is, went away.

[Sonny Disposition]

You should still aerate at night-- it would probably be better for the fish and the plants. Think of what happens if you add hydrilla to your unaerated bucket of shiners and then you cover the bucket.

[150EH]

My nano tank has a little Red Sea HOB filter and to make matters worse I use a sponge pre-filter on the intake to help keep shrimp fry safe, after just 2 weeks the pre-filter will get dirty enough that the filter no longer has enough flow to keep the water oxygenated, a surface film develops and I've even seen all my pest Ramshorn snails floating on the surface gasping for air. I think this could be one of the reasons your tank is having a problem if it is planted so densely the flow comes to a halt or just doesn't make it to all areas of the tank.

I don't have anything against aeration except to say of you don't have a lid on the tank those little bubbles popping will trash your drywall or wooden tank valance, etc. good luck with the cure.

[SCMurphy]

The surface film is fats and proteins and the snails are eating it.

[Sonny Disposition]

Yeah, try to keep that film from accumulating. Diana Walstad contends that it's a haven for Mycobacterium marinarae, aka fish tuberculosis.