Monitoring pH issue - The Planted Tank Forum
 
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post #1 of 5 (permalink) Old 03-21-2013, 10:27 PM Thread Starter
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Monitoring pH issue

Hi everyone,

I am struggling to figure out the pH of my aquarium. I have used different methods with very different results. I am inclined to believe the first way over the second since it is a new testkit, but what would you say? Please note that I have co2 running at 2-3 bubbles per second. Also, is the pH changed by the CO2 considerably?

Liquid API testkit: 6.4 pH
Digital reader: 5.7

Thanks!
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post #2 of 5 (permalink) Old 03-22-2013, 12:19 AM
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What is the KH?
Do you have any other buffers in there?
Any pH altering products?

Have you calibrated either test?

pH will follow the chemistry of whatever is in the tank.
Carbonates act to stabilize the pH, so that even if a lot of acidic reacting material is added, the pH tends to bounce back to its original level if there is a lot of KH.
Phosphate pH buffers are also common, especially in tanks that are for wild caught fish from acidic water.
CO2 tends to lower the pH, but the effect is variable: If you have a lot of carbonates, then the pH won't vary as much as a tank with very low KH.
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post #3 of 5 (permalink) Old 03-22-2013, 03:08 AM Thread Starter
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Thanks for your response! To answer your questions:

gH: 2, maybe 3
kH: 2

No other buffers or pH products. The digital reader was calibrated when I got it.
I suspect, then, that it must be re-calibrated now and then to read properly?
Both readings were taken at the same time.

Edit: Upon re-calibrating the digital reader, it came much closer to the api testkit, reading 6.2-6.3. Thanks Diana!

Last edited by Lee04; 03-22-2013 at 03:28 AM. Reason: Update
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post #4 of 5 (permalink) Old 03-22-2013, 02:22 PM
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Quote:
Originally Posted by Diana View Post
CO2 tends to lower the pH, but the effect is variable: If you have a lot of carbonates, then the pH won't vary as much as a tank with very low KH.
Unless you're referring to water that is totally devoid of carbonates, the effect of CO2 on pH is totally dependent on the amount of CO2 added no matter what the level of kH. 30 ppm of CO2 will drop the pH by the same amount whether you have 1 dkH, 10 dkH, or more. The only thing that varies is equilibrium pH and ending pH.

Dave

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post #5 of 5 (permalink) Old 03-22-2013, 07:05 PM
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I see no reason to monitor pH in a normal, run of the mill planted tank. If you don't monitor pH you aren't tempted to add stuff to the water trying to "correct" the pH, and that will almost always be better for the fish. If you have problems, and can't tell what is causing them, measuring pH is one of the bits of information that might help. Otherwise, it is counterproductive. (Just my opinion.)

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