# general hardness question



## Anafranil (Mar 15, 2005)

I am having a couple of questions regarding general water hardness that I hope someone helps me with it.First what do we measure when testing with a liquid tester,Ca and Mg cations or CO3 and SO4 anions?Is it the total charge of the ions that we measure or the molecular weight of the dissolved minerals that are in the water?I know that there might be other minerals in the water but of what I know most of them are the substances mentioned above.The reason I am asking these questions is that I found out that the value of my gh is the same as the kh and I am wandering if caco3 is the only mineral in my water.If this is true i am conserned about mg deficiency.My water is very soft(gh=4,kh=4)

thanks


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## Salt (Apr 5, 2005)

My understanding is most GH test kits are EDTA chelation tests. They react _only_ to calcium and magnesium ions. They also react _equally_ to calcium and magnesium ions. (This information comes from a chemist.)


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## Anafranil (Mar 15, 2005)

What I am thinking of is that in the case of kh we are definately interested in the co3 anion since this is responsible of the ph value when we ingect co2,so this is what should be measured.This is why i am sceptical about what you said and because kh is part of gh.


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## shalu (Oct 1, 2004)

The typical kh and gh test kits both report numbers as contained in EQUIVALENT CaCO3. GH kits measures the total charges produced by Mg++ and Ca++, and then assume it is all from Ca++ in CaCO3 and gives you the equivalent ppm of CaCO3 producing those charges. It does not mean you have (only) CaCO3 in the water, you could have MgSO4 dissolved in the water for example. Does that make sense? The only way to know how much Ca and Mg separately is to do another separate Ca measurement. GH and KH numbers do not match in general, but if they are predominantly produced by CaCO3, then the numbers are close, due to the way KH and GH are reported(first line in this post). But the reverse is not necessarily true. You can artifically add KH as baking soda NaHCO3, which does not change GH at all, and add CaCl2/CaSO4/MgSO4 to change GH without affecting KH, to make KH=GH. But in reality, your concern COULD be true, only additional testing can tell you.

That said, Tom Barr has been saying that he has never seen Mg deficiency in any tanks apart from intensionally inducing it several years ago.


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## Anafranil (Mar 15, 2005)

Completely understood,what i am thinking now is that if i use mgso4 to raise my gh a couple degrees I would have much more mg++ in my tank than the fertilator recommends,is this ok?
Of what i understand gh is important to the fishkeeper as some fish have different osmotic reactions since they live in harder/softer water.The question now is does it effect osmosis what element causes the hardness?For example if you use mgso4 instead of other substance to raise gh does this mater to the fish?


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## shalu (Oct 1, 2004)

I am no expert on fish physiology, but doubt fish is going to complain at all. However, why do you want to add so much Mg, vs Ca? Plants need far more Ca than Mg anyway. So you only need to add a little bit epsom salt for Mg(say, 1dGH or so), for your peace of mind, knowing you won't have Mg deficiency. Not to the extent of overwhelming the Ca concentration. You can use CaCl2 to increase GH more if you want to.


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## Anafranil (Mar 15, 2005)

that's what I did,thanks


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## plantbrain (Jan 23, 2004)

Anafranil said:


> I am having a couple of questions regarding general water hardness that I hope someone helps me with it.First what do we measure when testing with a liquid tester,Ca and Mg cations or CO3 and SO4 anions?Is it the total charge of the ions that we measure or the molecular weight of the dissolved minerals that are in the water?I know that there might be other minerals in the water but of what I know most of them are the substances mentioned above.The reason I am asking these questions is that I found out that the value of my gh is the same as the kh and I am wandering if caco3 is the only mineral in my water.If this is true i am conserned about mg deficiency.My water is very soft(gh=4,kh=4)
> 
> thanks


Your water is perfect.
You add about 1/8 teaspoon per 20 gal of MgSO4, epsom salt once a week when you do the water change. That would rule oout any Mg issue, but I doubt you'll have any.

Call up the water company and see what the Mg level is.
You can also estimate what the Mg by knowing what the Ca++ level is.

Regards, 
Tom Barr

3rd annual Plant Fest July 8-14th 2005!
[email protected] Get connected
www.BarrReport.com Get the information Now in Russian!


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## Anafranil (Mar 15, 2005)

The tests of Ca++ I've seen in the market are for marine tanks so I don't know if they show the range I am interested in.I never measured Ca++ before


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