Can't get a Gh reading... - The Planted Tank Forum
 
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post #1 of 7 (permalink) Old 09-17-2015, 04:39 PM Thread Starter
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Can't get a Gh reading...

My tap water seems to have zero Gh, Kh 27-28. I use 3/4 Ro/DI, 1/4 tap. I dose E.I. On weekly water water change, I add two tbs. Equilibrium (80 gallon tank, change half the water. API test Gh kit starts out pretty much colorless and stays that way, can't tell green from yellow. Bought a ELOS Gh kit. Supposed to start off red, then change to green. No red at start of test, light yellow to green as more drops are added.
AquaSoil now in the tank for 18 months, good plant growth, fish so-so after they get established.
What am I doing wrong on the Gh test?
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post #2 of 7 (permalink) Old 09-17-2015, 07:20 PM
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The GH test is the most problematic. If the test is ever stored where the temperature gets high then it is defective and will no longer work. Often they are bad before you purchase them. I have never gotten a kit that worked yet, although I have seen examples of other peoples tests on line.
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post #3 of 7 (permalink) Old 09-17-2015, 09:03 PM
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Hmm, I've not had trouble with my kit... but that's a sample of 1 kit..

Regardless, the API test being colorless is problematic.. Are the drops colorless? They should be very dark green coming out of the bottle... I could see having a hard time detecting the color in the first few drops, but by the time you get to 10 drops the color is quite pronounced.

For low drop counts I do suggest viewing them in a well lit room, with a white sheet of paper as a background. Stand the tube on the paper, and stand over it, looking diagonally down through the tube. (viewing diagonally increases the amount of water you are looking through and darkens the colors).

A bit like this:


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post #4 of 7 (permalink) Old 09-18-2015, 03:36 AM
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Quote:
Originally Posted by mattinmd View Post
For low drop counts I do suggest viewing them in a well lit room, with a white sheet of paper as a background. Stand the tube on the paper, and stand over it, looking diagonally down through the tube. (viewing diagonally increases the amount of water you are looking through and darkens the colors).
+1.

For very low GH readings, I find it easier to use 10-20ml samples.

Instead of using 5ml of water and using the number of drops as a result, you can easily use 10ml of water, and then divide the number of drops by two for the result. 20ml of water and divide the drops by four.

Feel free to edit.
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post #5 of 7 (permalink) Old 09-18-2015, 04:31 AM
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What kind of test tubes are you using for 10 or 20 ml? The ones bundled with the tests seem to be too small for this. Also, while increasing precision of the results, shouldn't it make color reading even more difficult as one drop of the test solution will be dissolved in even more water?
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post #6 of 7 (permalink) Old 09-18-2015, 04:39 AM
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30ml measuring cup for medicine. GH and KH don't need to be shaken, only stirred (thanks miss moneypenny).

The method is more suited for low measurement accuracy, but subjectively I would say also slightly easier to see the color change. Following mattinmd's method makes all the difference. ;-)

Feel free to edit.
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post #7 of 7 (permalink) Old 09-18-2015, 11:27 PM
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I have never seen such distinct colors as posted by mattinmd.
The ones that show up almost orange in this thread are clear or just a hint of yellow in my tests. The green is such a subtle shift it is very difficult to tell, especially if there is any green anywhere in the room, or even outside (I often read test results near a bright window).

Ditto the other answer that the GH test ages the fastest. When it is too old it will not turn any colors.

I will often do the test this way:
Half as much water (2.5ml) then double the results- one drop = 2 degrees. Sure it is less accurate. If I have a tank that I want to fine tune I can always start with more water.

To test the test kit:
Add Seachem Equilibrium to a small amount of water and shake a lot. Then test. If you get no response then you know the kit is too old.
Try adding the 2 tbs you use for water changes to a cup or two of water. Take out just enough to test, and you can use the rest in the tank.

Per Seachem web site:
1 tablespoon per 20 gallons = 3 degrees GH.

Kitchen math:
1 teaspoon per 6.67 gallons = 3 degrees GH.
1/2 tsp/3.33 gallons
1/4 tsp/1.665 gallons (call it one and a half gallons- close enough!)

If you start with distilled or RO water, it should change with the first drop.
Then make up that mix and it ought to change on the 3rd drop.
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