# I want a good electronic KH-GH monitor



## bsmith (Jan 8, 2007)

I see the drs has a few but im really not sure what TDS (total dissolved solids) equates to. Im tired of putting in a drop, capping, shaking, then straining to see what it has changed to. 

Testimonials would be very helpful.

Thanks.


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## wkndracer (Mar 14, 2009)

TDS measures everything in the water GH and KH


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## bsmith (Jan 8, 2007)

So how would that help us if we can tell where it comes from? For example, when I get a reading that indicates TDS are low. How do I know if I need to dose Ca or Mg?


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## wkndracer (Mar 14, 2009)

bsmith782 said:


> So how would that help us if we can tell where it comes from? For example, when I get a reading that indicates TDS are low. How do I know if I need to dose Ca or Mg?


It doesn't. 

The only place I measure TDS is my R O unit when the product water TDS number rises I know my filters are dirty and passing material. TDS is used more for saltwater.


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## bsmith (Jan 8, 2007)

So there is really no easier way to tesk these parameters then my API test kit?


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## epicfish (Sep 11, 2006)

bsmith782 said:


> So there is really no easier way to tesk these parameters then my API test kit?


No sir.


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## plantbrain (Dec 15, 2003)

Lamotte Hach test kits run about 15-20$ and are accurate to 4ppm or so.
You can go farther and do 2x the volume and take you time and get it to 2ppm.

Colormetrically, you have to go to a colorimeter to get better resolution for more accuracy, the Hach version can go more accurate with titration also.

0.01 ppm.

I think the KH/Gh test kits are fairly decent overall.
The method rarely is off by much and if you use 2x the volume for the sample, you count each drop as 0.5 degrees instead of 1.
So you are at about 8ppm.

Not bad for most things.
GH = total Ca and Mg.
Ca test kit = Ca, then subtract the Ca for Mg.

Back check the KH, see if the standard is the same as the reading from your tap water smaple.

Say the tap/Tank water says 2 KH.
Then take some 4 KH reference solution, dilute by 50% with DI water.
Test again. Should be 2 KH etc.



Regards, 
Tom Barr


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## KevinC (May 24, 2004)

Calcium ion-selective electrodes (ISE) are available - they work in much the same way a pH meter does. There are several problems though - other ions might interfere (give a false high or low reading) and they require frequent (perhaps with each use) calibration. They are also logarithmic in response, so the error can be higher than that of titration. You might not think they are easier to use than the kits. 

I'm not sure if I've ever seen a Mg-ISE. Of course kH cannot be measured in this way since it is a performance parameter, not a specific chemical parameter.


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## bsmith (Jan 8, 2007)

Good info guys.


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## wkndracer (Mar 14, 2009)

*A question of my own*

I've read into this subject due to my own water problems in the past. Along with the three different active threads. The KevinC post looks to be informed information. Its also the first I've seen separating Ca and Ma in GH testing with electronics. Cost and equipment calibration still seem to be problematic. 

Can I please ask as I haven't seen it posted, what is the driving force to separate Ca, Ma in testing GH?


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## Hoppy (Dec 24, 2005)

This is an example of why a fertilizing system that involves adding specific amounts of everything routinely, then "resetting" the water by doing a big water change routinely, is such a great way to go. I can't think of any water parameter, other than CO2 ppm, that we need to monitor carefully to keep within certain limits. We just need to make sure we have enough of each, without having an extreme over supply.

Unfortunately, the one parameter we can benefit by keeping within close limits, CO2, is also the hardest to measure and to maintain at a specific value. But, that just makes the hobby more challenging.


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## bsmith (Jan 8, 2007)

When I made this thread I was under the assumption that KH was directly related to the amount of Ca/Mg and GH was directly related to the amount of Ca/Mg I just didnt know which one was which.

Now I see that is not true.


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## wkndracer (Mar 14, 2009)

Thanks for the rely! _Ahhh Sooo says the blind man_.
My tank readings over 1-2 weeks always read a rising GH so the water changes consisting of distilled water (because my house water is crap) only reduced the 'hardness' of the water but did nothing to replace minerals. The tanks never got back down to 2dGH or 3dGH so minerals could be added back. With single water changes of 20 - 30 gallons on a 75g tank with a GH reading 8 or above the hardness would not reset low enough to add back.
While I had a GH reading my plants suffered. Research didn't uncover an analysis method that wasn't insane that would tell me which was missing either Ca or Ma. I started 50% weekly water changes with R O adding GH booster. (settled on Rex's Grumpy mix based on cost) and within a month the issues went away. I also found out through use Grumpy's dissolves way better in the tank than Seachem Equilrium.


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