Baseline pH when using peat, driftwood, and CO2 injection - The Planted Tank Forum
 
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post #1 of 3 (permalink) Old 02-13-2006, 02:33 PM Thread Starter
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Question Baseline pH when using peat, driftwood, and CO2 injection

I started up my first CO2-injected planted tank a little over a week ago and I'm trying to find the optimal amount of CO2 injection, but the addition of peat under the substrate and driftwood make it difficult to gauge the CO2 concentration using the "chart."

Here are my water parameters:

kH - 4
gH - 6
straight tap water pH - 6.8
tap water outgassed overnight - 7.1

This weekend, I had an accidental CO2 overdose turning my tank into a bubbling acid pool (luckily I didn't lose any fish). Leaving the CO2 off for two days and performing three water changes (50%, 25%, 25%), the pH is now at 6.3. That seems pretty low, so I'm not sure if the CO2 is completely outgassed yet, or if that is really my tank's baseline pH.

Will a cup of tank water left overnight reflect the pH drop from peat and driftwood, and provide a 0 ppm CO2 baseline pH? That is, will the difference of pH between this baseline and the actual tank pH be solely due to the injection of CO2?
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post #2 of 3 (permalink) Old 02-13-2006, 04:45 PM
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My understanding is that a cup of tank water left out overnight will give a PH about one unit higher than the daytime tank value if you have around 30 ppm CO2. I have a very thin layer of peat moss under my substrate, which I had forgotten about, and which may be why my CO2 measurement from KH and PH may be so far off. But, the overnight tank sample does go up in PH around one unit, so I am assuming I am ok.

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post #3 of 3 (permalink) Old 02-13-2006, 05:31 PM
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Quote:
Originally Posted by turbowagon
Will a cup of tank water left overnight...provide a 0 ppm CO2 baseline pH?
Water that has had a chance to age and outgas should hit a level where CO2 is around 3 ppm. That's the rule of thumb I've read in many places.

Quote:
Originally Posted by turbowagon
That is, will the difference of pH between this baseline and the actual tank pH be solely due to the injection of CO2?
Yes and no, IMO. For that point in time, yes the difference will mostly be due to CO2 outgassing. However, with both peat and driftwood in the tank, I would suspect that your KH levels are likely fluctuating, most likely dropping. And, as the KH fluctuates, assuming a constant CO2 level, so fluctuates the pH. So, you might want to start regularly mapping your KH levels also to see how quickly they are fluctuating.
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