Data on Gas Exchange - Glass Covered Tank

[Quietman]

Looking for any data for gas exchange in reef tanks (or aquariums in general). I'm curious because I run my freshwater tank with glass cover with openings in the rear for equipment. Evaporation is reduced to the point where top-off is only once a few liters once a month. Compared to my reef tank running at lower temps and slightly smaller surface area with roughly same surface agitation, this is a fraction of the 15-20 gallons a month it takes for top off. I understand there are differences in evaporation rates and O2/CO2 consumption which is why I'm looking for data.

Basic questions would be how much of an opening does it take to provide sufficient gas exchange between under the lid and the indoor atmosphere. Different CO2 levels indoors assume to be negligible impact (yes, it's impact but would be if covered or not).

My intuition is that a covering sufficient to reduce evaporation significantly but still having a few small openings for equipment would provide sufficient exchange with air outside the tank to the point that there would be no difference between that and my mesh screen top. Adding a skimmer or air stone (ATS) would just further reduce impact of a glass cover.

Anyway just wondering if someone has data. O2 meters (good ones) are expensive and probably not something most hobbyists would have, including this one.

 

[vlangel]

I worked for a lfs taking care of their tank accounts. My boss set nearly all his tanks up with glass tops and plastic attachments that could be cut out for equipment. There was very little openings so that fish could not easily jump out. With HOB pumps and a powerhead,(which is how a lot of tanks were set up in the 90s) even then there was plenty of oxygenation in the water as long as there was surface agitation. My own tank has a glass top as does my sump with only a small amount open to the air. I only go through 1 gallon a week as oppose to almost a gallon a day before the glass cover.