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pH-KH-CO2 Table

What about measuring pH twice :

1. in the tank
2. after two days of rest in a bucket


Where does the 3ppm concentration of CO2 in the bucket come from ?
Does it depend of temperature ?



Date: Fri, 14 Dec 2001 09:25:09 -0500
From: "Doug Karpa-Wilson" <dkarpawi at indiana_edu>
Subject: pH-KH-CO2 Table


In a word yes.  The table assumes that the only buffer system in the water
is the carbonate buffer system, and adding another buffer will throw off the
calculations.  I hadn't seen the "extreme measures" clause, but I wish Eric
hadn't put that in there.  In my experience, *every* single time the table
is checked against readings from a higher end CO2 kit, such as the LaMotte
kit, the table comes out too high, sometimes ridiculously so.  If that table
were accurate, either my fish should be dead, or they're all some mutant
strain that can handle CO2 concentrations of up to 400 ppm with only a DIY
bubbler. Somehow I don't think so. Plants produce all sorts of changes to
water chemistry which I'd be willing to wager also throw off the table.
Now, one very important caveat is that my tanks are often below ph6, where
the table is very, very sensitive to small errors in pH measurement.
perhaps the table's more useful around or above a pH of 7, but even then,
you'd really need to have a good pH measure.