GH KH TDS - how to measure - The Planted Tank Forum
 
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post #1 of 12 (permalink) Old 07-04-2015, 03:46 PM Thread Starter
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GH KH TDS - how to measure

Here are the tools I have:
* API KH kit
* API GH kit
* electronic TDS measuring tool - $20 or $30 purchase


I'm done mutiple measures.
First measurement: KH 2, GH 12[?], 80 TDS

after adding 25% pure RO in a 55g i get: KH 1, GH 12-15[?], 41 TDS

i am suspicious of my GH kit (or my ability to read it) and/or the TDS tool. is there any alternative way of measuring these 3 values specficially GH?
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post #2 of 12 (permalink) Old 07-04-2015, 04:27 PM
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Sense your TDS lowered, your GH should be lower.

Are you holding the bottles completely upside down so that the drops are the correct size?

Holding the bottle sideways will make the drops smaller than they should be.

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post #3 of 12 (permalink) Old 07-04-2015, 04:47 PM Thread Starter
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noted about holding bottle directly upside down... (i dont know - probably not) but it should have have such a large effect? im guessing my GH is like 4-6 range.

also ive never seen GH turn GREEN.. its more "yellow green" - going from golden yellow to dirty yellow at around 13 14 15 drops. is that what they call green?
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post #4 of 12 (permalink) Old 07-04-2015, 05:01 PM
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At 41 ppm TDS your GH is probably between 2 and 3 degrees. That is very very soft water. If you go much lower then plants will begin to suffer lack of minerals.

If no other solids are dissolved besides the minerals then divide ppm by 17 for an approximation of degrees of hardness. Tank water always has other things dissolved in it such as nitrates from food and waste so actual mineral TDS would be even lower.
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post #5 of 12 (permalink) Old 07-04-2015, 06:00 PM Thread Starter
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for GH API test kit i am consistently getting slight yellow to yellow-green color change after 10 drops. something wrong with the kit? something wrong with me? what else could be wrong?
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post #6 of 12 (permalink) Old 07-04-2015, 06:09 PM
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If your not sure of the color, take the cap off and look down through the test tube.

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post #7 of 12 (permalink) Old 07-04-2015, 11:13 PM
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The GH test is the most problematic. I have never had one that worked properly. The one I have now you could add the entire bottle and never get a change. It has been that way since the day I bought it. There was another thread talking about this the other day, I think in the sticky on test calibrating and it was mentioned that if the test was stored in too high of heat that it might make it inaccurate.
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post #8 of 12 (permalink) Old 07-05-2015, 12:08 AM Thread Starter
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hmmm. mine's always stored in cool basement.

are there any KH GH units where i dont have to continously buy liquids to test? i would rather pay 100 or even 200$ for an accurate on-demand method of testing if i dont have to buy additional solutions.

sort of like an electronic tds or ph meter
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post #9 of 12 (permalink) Old 07-05-2015, 01:03 AM
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I do not know if there are probes for GH.

There are other companies that make GH test kits, including more test-tube-reagent type, and dip stick types.

Some of the other companies' tests read in different colors, perhaps easier to read.

Are you on a well? Or municipal water supply? If it is a public supply there ought to be a water quality report.
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post #10 of 12 (permalink) Old 07-05-2015, 02:42 AM
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You're probably having trouble reading the GH test because it is changing color with the first drop, and the less drops needed for the color change, the fainter the color is.

TDS 41 ppm = 2.3 German degrees. Since this is the total dissolved solid reading, it not only reads Ca2+ and Mg2+ (GH), but everything else also. CO3, HCO3, K, Na, Cl, Fe, PO4, SO4 among others.

Since you don't have a problem reading the KH test, and the result is 1 dKH (17.848046 ppm), this leaves 23.152 ppm (1.3 dGH) of other dissolved solids (give or take).

In typical aquarium water, GH is basically only Ca2+ and Mg2+. If you have any K, Fe, NO3, NH3, PO4, SO4 (among others), this detracts from the 23.152 ppm of dissolved solids above. Leaving around 1 German degree (17.848ppm) or less of GH.

Last edited by Audionut; 07-05-2015 at 03:05 AM. Reason: Clarity regarding ions
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post #11 of 12 (permalink) Old 07-05-2015, 04:42 AM
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For what it is worth, these are the kind of colors I get out of my GH test kit, on water that I've "hardened up" with equilibrium...



Note: I've taken these shots in conditions that maximize the color.. looking down from a bit of an angle, with a white paper background, and plain white light overhead, and at night to avoid sunlight reflecting off plants from throwing the color off.

Regardless, mine really does get those colors when viewed at these angles... Running the test on softer water obviously gets less dark of a color reaction.

At least one person here (Diana) has commented that she never got colors nearly that dark...



All that said, I do agree there's a major disconnect between 12 dGH and 41ppm TDS... At least one of those numbers has to be wrong.

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post #12 of 12 (permalink) Old 07-05-2015, 05:55 PM
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If GH is that low and thought to be unmeasurable.
Double the test volume to 10ml. and divide by 2 the drops.


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Growing is not that difficult.
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