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Old 01/15/2017, 09:27 PM   #17
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Originally Posted by karimwassef View Post
Datapoint. I was curing ~100lbs of concrete in my tank (before life).

The starting pH was 11
I turned on my very large skimmer
pH dropped to 9 very quickly and then stabilized to 8 within a few hours.

This was in ~500gal of tap water.

I kept this up for a couple of weeks - pH never went above 8.3. I would occasionally turn the skimmer off to test the "curing"

math problem: how much CO2 does it take to do that and how is it that this abundance of CO2 is not available to algae?

My conclusion - as quickly as the algae (or in my case concrete) consumes CO2, it is replenished - the state it is in CO2, carbonate or bicarbonate doesn't matter.
So what youíre saying above, is, that without artificial diffusion of CO2 into the tank water via aeration by protein skimming, the pH would settle at 11. Natural diffusion, by the partial pressure of CO2 in the air in the vicinity of the tank was not fast enough to maintain the pH below 11. The lime water consumed it too quickly.

This is the point Iím making in regards to my aquarium, & SantaMonica pointed out earlier. The algae in my scrubber consumes bicarbonates faster than the natural diffusion of CO2 can replace it until it has dropped to 125ppm where an equilibrium has been reached.

Equilibrium was reached, at a pH in your case, of 8.3, by artificial diffusion via skimming aeration. No higher, no lower.

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