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Re: Aquatic Plants Digest V3 #365

In a message dated 98-07-05 16:18:43 EDT, I wrote:

<< On Sun, 5 Jul 1998, RDotta7777 wrote:
 > When I hook up my CO2 system (using a pH meter to trigger the CO2
 > the water after a water change has a pH of approx 6.2.  I then allow the
 > to bubble in (at a slow rate).  In about 15 minutes my 125 gallon tank has
 > new pH of 6.1 and the system shuts off.  The pH never comes back up to re-
 > trigger the CO2.  I have to add Sodium Bicarbonate to re-adjust the pH to
 > the CO2 back on.  I have to do this every day.

Roger replied:
 This is rather odd behavior.  Not implausible, just odd.  So, instead of 
 answering the question I have to ask two more:
 What is the buffering capacity of the water you're using?
 Have you calibrated your pH device and/or checked its results with a 
 chemical indicator? >>

It seems that the buffering capacity is the issue.  The water measures a
Carbonate hardness of 40ppm with the LeMotte test kit which I equated to a dCH
= 5.06.

I just recently (two days ago) recalibrated the pH meter.  

I think that the water's buffering ability is low, but it seems difficult to