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Do you take the 1 pH drop from completely degassed water or from just before CO2 turns on?

Hi all,
since 6CO2 + 6H2O → C6H12O6 + 6O2 you could also measure dissolved oxygen real-time? Higher dissolved oxygen would correspond with higher Co2 uptake
You can, <"highly productive systems"> will have larger oxygen production. If we aren't adding CO2, we can <"use the pH readings"> as a proxy for the CO2 : O2 ratio.

In an "added CO2" scenario we would have to use plant growth as the measure of CO2 incorporation (and the consequent oxygen production). Have a look at the <"linked paper for some more discussion">.

cheers Darrel
 
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22802is right, O2 degassing will make the calculations invalid. It's true that with higher photosynthesis you get higher O2 levels. It's a good indicator and allows comparison within the same system provided that temperature and 'surface disturbance' remain the same. It's not reliable to use as input for stoichiometry.

The more oversaturated the water is the quicker O2 will degas, it's not a constant. The more oversaturated the water is the more O2 will form "pearling" and thus not be accounted for before it escapes to the atmosphere etc.
 
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hi all,

Went an installed a makeshift wet/dry sump.

Long story short: fish had rapid breathing (they were not in harm), I wanted it slower.

Built the sump, within an hour - rapid breathing finished.

The O2 is real.
The sump increases the overall water surface and the gaseous exchange rate. If you kept the same CO2 injection rate, then it is expected that the CO2 concentration decreased and O2 concentration increased. In any case, you do not need a sump to achieve this effect, although a sump or a trickle filter are arguably one of the easiest ways to promote gaseous exchange.
 
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