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1) Response time for a drop checker.

2) Surface area/flow required to diffuse a set amount of CO2.

This brought me to Fick's Laws of diffusion.

Per Wikipedia: http://en.wikipedia.org/wiki/Fick's_law_of_diffusion

flux=-P*A*(c2-c1)

A = transfer area, I can calculate that.

c2-c1 = the concentration difference. In the case of pure CO2 it is 1, for the aquarium water or drop checker it will be ~0.000030 (30PPM).

Unfortunately, I don't know P. I'll worry about reactor bubbles later, but for now I'd like to figure it out for the drop checker. I'm assuming this has something to do with surface velocity, and seems like it should be a known property for CO2/water. Can anyone point me to tables (or anything else) for this?

Also, any advice on calculating the CO2 concentration within the air of the drop checker? Is it the same as the aquarium, or higher? My first guess was the same, but if you think of your aquarium as a giant drop checker then that would imply %CO2 in the aquarium == %CO2 in the air, which is not true.