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Discussion Starter · #1 ·
Can somebody help me calculate KG and GH from my water district report? They report:

alkalinity-total (CaCO3)=24 mg/L
hardness (CaCO3)=38 mg/L
Calcium (Ca)=14 mg/L
Magnesium (Mg)=0.72 mg/L

I'd really like to translate these values into degrees and know which is KH and which if any translates into GH. Also is mg/L the same as ppm?

Thanks,
Grant
 

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Hagen has an online conversion utility

Now the sticky part

Useing mg/L can be more accurate then kH and dh reason being that you need to know what form of degree you are using.
1 German degree = 17.9 ppm (as CaCO3)
1 American degree = 17.1 ppm
1 English degree = 14.3 ppm
1 French degree = 10.0 ppm

In general the majority of the test kits we use in the hobby report as dkH or German degrees
 

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Discussion Starter · #3 ·
KH confusion

Let me amend my initial query to clarify my confusion:

What is the difference between alkalinity-total (24 mg/L) and hardness (38 mg/L) when they are both listed as CaCO3? Furthermore, is one of them equivalent to KH? And, can GH be calculated by knowing the Ca and Mg concentration (14 mg/L and 0.72 mg/L respectively)?

My goal is to figure out what my tap water offers using the data available instead of getting more test kits. Am I right that this water is very soft?

Thanks,
Grant
 

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Ok I'll give this a go. Someone chime in if I've got it totally wrong!

alaklinity is usually linked to KH and hardness to GH. They list CaCO3 because ppm or mg/l readings are measured "as" CaCO3.

Yes, GH can be calculated like that if you assume that the Ca and Mg makes up the majority of your GH. Use this forumula:

(mg/l Ca / 7.2) + (mg/l Mg / 4.4) = dGH

In your case, this works out to around 2.1 GH. Converted to CaCO3 ppm equivalent (x 17.9) this gives 37.6 ppm CaCO3, more or less matching your 38mg/l hardness reading...

So your tap water has a KH of 1.34 and a GH of 2.1. That is extremely soft water. You also have a low percentage of Mg as related to Ca so I would say you also need to add Mg for plants...

Hope this helps a bit! :D
 

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Discussion Starter · #6 ·
Thanks to Laith!

That's exactly the info I was hoping for--although I'd prefer that my water wasn't so soft. I hope you're right with your math, but it about matches what I was able to figure without really knowing...

Given my KH and GH numbers, does it make sense to raise both using calcium carbonate and dose MG using epsom salts? Other suggestions? I'm also curious if anyone has a timetable for raising these to suggest.

Thanks a lot,
Grant
 

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Consider yourself lucky that you have soft water! :) It is much easier to harden soft water than to soften hard water...

I recommend using both Ca and Mg to raise GH, trying to keep them in a ratio of around 3 or 4 (Ca) to 1 (Mg).

Calcium Carbonate will raise both GH and KH but I find it takes forever to dissolve and have any impact and I get impatient easily! :D

So I use a combination of CaCl (Calcium Chloride, you can also use CaSO4) and MgSO4 (Epsom salts) when I want to raise the GH. All of these dissolve pretty easily. These will increase GH only.

For raising the KH I use sodium bicarbonate (baking soda). You will want a KH of at least 3 to be able to buffer your pH adequately, especially if you inject CO2. Baking soda will only raise KH (and consequently, your pH will go up a bit).
 
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