Looks like Tom has answered the question
Quote:
Originally Posted by Tom Barr
The solubility of free CO2 increases when you have lower KH's.......but that's not really an issue for us if we enrich with CO2 as it's pretty soluble to begin with.
This affects the rate that CO2 comes in/out of solution, not the CO2 ppm at equilibrium.
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If CO2 solubility decreases with increasing KH then you get higher CO2 loss at water's surface and also slower dissolving of CO2 means more bubbles reach the surface and are lost to the atmosphere. What does this mean? You need a higher CO2 injection rate to obtain the same CO2 levels in a high KH tank than you do in a low KH tank.
Equilibrium levels of CO2 aren't being disputed, and are the same in different water samples having different KH's. What is being suggested is that at above equilibrium levels of CO2 there is a greater loss CO2 in water of high KH compared to one with a low KH.
Big question is how much of a difference does it really make within the KH ranges we see within our tanks? Might be worthy of an experiment
James