Ph Test Question

**shloken38** · 10-11-2012, 10:04 PM

I am not overly concerned about this, just a bit curious. When I test with the API low ph test, I get blue, 7.6. I then test with the API high ph test kit and I get brown, 7.4. How exactly would you interpret that? It's always the same in each tank, so it's consistent and not really a problem. All other parameters are good. Thanks for any answers!

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**mesto** · 10-11-2012, 10:53 PM

Doesn't the low pH go from 7.2 to 7.6 at the high end and the high pH goes from 7.4 to 7.8? It would seem color accuracy is less at the edge of each range, where the colors shift not much for a 0.4 change n pH. In the middle of each test fairly large color changes relate to 0.2 change in pH so those ranges are obviously more accurate. I would call it 7.5.

**shloken38** · 10-12-2012, 7:22 AM

Actually, the high test goes from 7.4 to 8.something. So basically I am getting the highest reading from the low test and the lowest reading from the high test. There's definitely no question in either color. Since my ph is consistent, I'm not really worried. Just curious about how to read it. Thanks for the response! Hopefully others will chime in as well.

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**mesto** · 10-12-2012, 8:26 AM

No, I know, I'm saying neither test is as accurate at the edge of the range. If you look at the color chart you will see that the low test is most accurate from 6.4-7.2, where each color change corresponds to just 0.2 pH. On the high pH test, the accuracy is highest from 7.8-8.4. Add to that the issue that 7.6 on the low test doesn't have to mean 7.6, that reading really just means, "out of range of test" since pHs of 7,6. 8.0, or 10.0 even would all test the same. same for the 7.4 reading on the high pH test. There's like a little "blind" spot between the two tests from about 7.4-7.6 where this would be expected to happen. So your pH must be about 7.5

**mesto** · 10-12-2012, 8:31 AM

ETA my original answer wasn't very clear, but I am looking at the scaling of pH readings at the ends of the test and how that differs from the middle ranges.

**shloken38** · 10-12-2012, 12:37 PM

Understood, and thanks much. I know that maintaining a consistent ph is the key, which I've been pretty good at. Don't know why, but this was just bothering me at the moment for some reason. 7.4 or 7.6.....doesn't really make much of a difference anyway.

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