CO2 during the day and Oxygen at night


Junior Poster
Jan 26, 2005
I recently began turning on an air pump at night for 4 hours after the lights and CO2 are turned off. I have noticed that the plants seem to be looking better, growing very fast.

My question is, if by adding CO2 during the day we are helping photosynthesis, can't we help respiration at night by adding some oxygen?

Tom Barr

Staff member
Jan 23, 2005
Re: CO2 during the day and Oxygen at night

No, there amount of O2 added at night will do nothing for the plants.
They have much less O2 demand/consumption than fish/shrimp etc.

The plant might be growing better simply because you have more current and you have a higher bioload(fish/shrimp).

Added current can help during the day also.

But adding O2 at night is not the issue, if you have decent growth during the day, even a well stocked Disacus tank with 2w/gal tends to not fall below 90% stauration, that is about at best what most aeration can do. Plants add pure O2, not 20% O2 from air.

So we get more than 100% during part of the night, then turning it on after it dips below 100% is not a bad thing, but I doubt that is the reason for better growth(adding O2 for the plants).

Tom Barr