Stupid questions about API GH and KH test

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captmicha

Le tired.
Dec 6, 2006
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Don't judge me!

For GH, it says the test is complete once the water turns from orange to green. It then says, in the next step, that it's determined by the # of drops that must be added to turn the water in the test tube to green. (Of course KH is the same but with different colors.)

Stupid questions are:
1. Does that mean that I don't count the first drop added to turn the water orange?
2. What if it takes a couple of drops of reagent until the water in the test tube turns orange? Do I not start counting until after it's orange? Or do I just assume that the first drop makes it a really light, hard to detect orange?

3. Everyone probably already knows this but the GH and KH share the same chart. So when I'm converting the number of drops for the GH test, do I discount the °dKH column?

4. If I got the number of drops right, am I even converting the results correctly?

GH took 6 drops, so would I convert it to 6°dKH and 107.4 ppm GH? Or would it just be 107.4 ppm GH?
KH took 3 drops, so would I convert it to 3°dKH and 53.7 ppm KH?
 

SubRosa

AC Members
Jul 3, 2009
5,643
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1. Every drop counts
2. Every drop counts
3. What "chart"? Color change is the only indicator. The two figures although very related should be considered individually at this point.
4. Multiplying KH or GH numbers by 17.86 converts to ppm, so your math is a bit off but not enough to really matter. I get 107.2 ppm GH and 53.6 ppm KH.
 

captmicha

Le tired.
Dec 6, 2006
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Maryland, USA
3. What "chart"? Color change is the only indicator. The two figures although very related should be considered individually at this point.
The GH & KH Conversion Chart that comes in the kit. This isn't the chart that came in my kit but maybe it's the new chart and mine was the old one... I dunno. KH and GH share the same chart in my kit. http://www.americanaquariumproducts.com/downloads/KH-GH-test-instructions.pdf

4. Multiplying KH or GH numbers by 17.86 converts to ppm, so your math is a bit off but not enough to really matter. I get 107.2 ppm GH and 53.6 ppm KH.
I followed what the chart said.
 

oo7genie

Hello my fintime gal...
Nov 18, 2010
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Eugene, OR
Real Name
Rick
Like Subrosa said. Every drop counts. It's really as simple as just counting them. The instructions overcomplicate things.

I personally just use the number of drops as my indicator and don't bother multiplying as most U.S. websites and resources list the GH & KH in these simpler units.

The reason your results are different than Subrosa's, is because he's using the more accurate multiplier of 17.86, and the API instructions rounded that up to 17.9. Either way can be considered close enough, when you consider each drop changes your results by nearly 18.
 

captmicha

Le tired.
Dec 6, 2006
2,052
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Maryland, USA
I didn't know about what to X the drops by so I just went with the chart but you're right, it seems close enough.
 
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