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Discussion Starter · #1 ·
I had been using a nutrafin gh/kh test kit. Today I picked up an API gh/kh test kit as my reagents from the nutrafin kit are almost used up. The two different kits give different results. The nutrafin kit measures in PPM, 5 drops to turn from blue to yellow(KH). You multiply by 10 to get 50 ppm, then you can divide by 17.9 to get 2.79dkh. The API kit, the drops are directly correlated to degrees. It takes 4 drops with the API kit so its 4dkh.

Which brand would you consider to be the more accurate? The api kit has much bigger bottles of reagents. Thats why I went with the API kit this time, they cost the same so the api would be a better value but not if it isn't accurate.
 

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I had been using a nutrafin gh/kh test kit. Today I picked up an API gh/kh test kit as my reagents from the nutrafin kit are almost used up. The two different kits give different results. The nutrafin kit measures in PPM, 5 drops to turn from blue to yellow(KH). You multiply by 10 to get 50 ppm, then you can divide by 17.9 to get 2.79dkh. The API kit, the drops are directly correlated to degrees. It takes 4 drops with the API kit so its 4dkh.

Which brand would you consider to be the more accurate? The api kit has much bigger bottles of reagents. Thats why I went with the API kit this time, they cost the same so the api would be a better value but not if it isn't accurate.
Considering the type of test (count the drops) the difference between 3 and 4 dkH is not that much. You cannot say which test is more accurate by looking at the bottle. The only way to tell is by testing an accurate known control.
 

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I had been using a nutrafin gh/kh test kit. Today I picked up an API gh/kh test kit as my reagents from the nutrafin kit are almost used up. The two different kits give different results. The nutrafin kit measures in PPM, 5 drops to turn from blue to yellow(KH). You multiply by 10 to get 50 ppm, then you can divide by 17.9 to get 2.79dkh. The API kit, the drops are directly correlated to degrees. It takes 4 drops with the API kit so its 4dkh.

Which brand would you consider to be the more accurate? The api kit has much bigger bottles of reagents. Thats why I went with the API kit this time, they cost the same so the api would be a better value but not if it isn't accurate.
Merely comparing the two won't tell you which one is more accurate, unless you have a reference solution with a known KH.

Nutrafin is much more precise and therefore reveals finer changes. In fact, using API I could never tell its GH (not KH) reading, but I have no problem with Nutrafin.
 

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Discussion Starter · #4 ·
It's true you can't compare accuratly without a set refrence. I was just sort of wondering if people prefered one brand over another. The nutrafin has fancy packaging and just looks like a better product but that can't be a perfect indication of quality. I have some distilled water, maybe I'll test that.
 

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You seem to be running low on reagent for the Nutrifin test kit, which suggests that it may now be too old. That will certainly reduce the accuracy of the result. But, Ray is right that unless you calibrate with a known set of standards you have to assume that any test is inaccurate to some unknown degree.
 
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