# How much Dolomite to increase KH



## Kypros (Apr 16, 2008)

I bought some Dolomite (Calcium Carbonate with Magnesium) from Aquariumfertizer.com to increase KH in my tank. My local water has registrable KH and I would like to make sure I have stable KH. Does anybody know a rule of thumb for the referenced product. How many grams in how much water to raise KH 1 degree?
some advice would be appreciated. Aquariumfertizer.com did not know.
thanks


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## Diana K (Dec 20, 2007)

I would run a test in a bucket. Carefully measure the product and the water volume. 
Test GH, KH and pH before you start, and daily for a couple of days, then run the test for a couple of weeks. 
Questions: 
How much did it take to get the results you want? 
Are the results stable over the length of time that might go between water changes? (Assume you will re-set the water chemistry with each water change)

As for how much to use... 
I would start with 1/4 teaspoon in 4 gallons (a 5 gallon bucket, not all the way full), and see if there is a measurable change. Keep the water moving (fountain pump or bubbler) overnight and test again. Sometimes the material does not fully dissolve, and you will not see the full change for several hours. If this is not enough, then you may at least have some idea as to amount to use. If 1/4 teaspoon in the 5 gallon bucket only created half the change you wanted, then double it. Remember to check GH, KH and pH every time until you see how they are altered with this product.
Once you find a recipe and method that works you will need to work it into your water change schedule. If it takes 2 days to dissolve and become fully active, then you will need to start preparing the water 2 days before a water change. 

I use baking soda. 1 teaspoon in a 29 gallon tank will raise the KH from 0 degrees to 2 degrees, and the pH will come up from 'bottom of the chart' to 6.2. The substrate in this tank will remove the KH over time, so I need to check it and add more baking soda frequently when I first set up a tank with this substrate. This does not alter the GH, though.


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## wet (Nov 24, 2008)

Feel free to correct me:

Dolomite is CaMg(CO3)2
CaMg(CO3)2 is 184.4 g/mol
I have 2 C's and 6 O's in there.
So
CO3 (what we care about for KH) is 65.1% of CaMg(CO3)2.
and we know
1 dKH = 10.7 ppm (mg/L) CO3

Let's say you have a 50 gallon tank (189 Liters).
Let's say you want to raise those 50 gallons by 1 dKH.

mg CaMg(CO3)2 = target dKH * 1000mg CaMg(CO3)2 / 651 mg CO3 * 189 L

(Or, the milligrams of Dolomite needed is the product of target degrees KH multiplied by tank volume then divided by the percent of carbonate in Dolomite.)

So:

mg CaMg(CO3)2 = 10.7mg CO3 / L * 1000mg CaMg(CO3)2 / 651mg CO3 * 189 L = 3106mg CaMg(CO3)2.

Therefore, I need *about 3 grams of Dolomite to raise 50 gallons by one dKH.*


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## Diana K (Dec 20, 2007)

1 German degree of hardness = 17.9 ppm


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## wet (Nov 24, 2008)

1 dKH is 17.9mg CaCO3/L. Above is calculated by CO3 (actual carbonate). CO3 is about 60% of CaCO3. So, 1dKH is 10.7 mg CO3/L.


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## Diana K (Dec 20, 2007)

Oh.


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