# Recommendations for KH



## andy485 (Aug 19, 2005)

Had this question on another post but did not get it answered. I am using RO water and reconstituting it with calcium chloride and magnesium sulfate. I have been told to also raise the KH by using baking soda. I believe it was 10.6 grams will raise 90 gallons by 1dkh. What is the recommended KH level? I have my PH controller set at high 6.4 and low 6.2. If I use baking soda and raise it to 3dkh will that be alright. This is one aspect that I have not learned about so if anybody can lead me in the right direction or show me were to read about KH and PH values as related to CO2 levels please let me know. My aquarium is pearling alot but I am a little worried that that could end soon and the algae bloom could follow if I don't get this right.


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## John N. (Dec 11, 2005)

This may help:.

KH is typically around 5-8 for me, and used to figure out a general CO2 concentration in the tank. Some plants prefer lower where some prefer higher. Shoot around 3-8 degrees, and work your pH levels to fit the CO2 chart.

-John N.


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## Salt (Apr 5, 2005)

Personally, I do 80 ppm (as calcium carbonate). I use potassium carbonate instead of sodium bicarbonate.

Also, your math is _way_ off. 1.399903 milligrams of NaHCO3 raises 1 liter by 1 ppm. Translating that to 1 dKH in 90 gallons comes to 5.10 grams. ([1.399903 mg * 3.785412 liters/gallon * 10.70109 ppm/1dKH * 90 gallons] / 1000 mg/g)


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## Cavan Allen (Jul 22, 2004)

> What is the recommended KH level? I have my PH controller set at high 6.4 and low 6.2. If I use baking soda and raise it to 3dkh will that be alright.


Yes, a KH of 3 would be fine. I use Seachem alkaline buffer to raise my tap from 2 to 3KH.


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## andy485 (Aug 19, 2005)

See this is what confuses me. I used to use tap water, my KH in my tap water was 8 and my PH is 7.6. So when I use my CO2 controller and bring my PH down to 6.4 and my KH is still reading at 8 closer to 9 my CO2 is over 100ppm yet my fish are still active and healthy. So when I mix my ro water with my tap at a 9(ro)to1(tap) ratio it drops my KH to 1. I have not tested my ph in my ro water I am guessing around 6. So if I bring my KH to 3 and keep my PH at 6.4 by using my controller will I have enough CO2? Can anybody tell me how to accurately figure this? Because if I am adding KH to 3 then the CO2 is not doing it, it is the baking soda, so then should my CO2 bring my KH to 6 which would be like 3 of the KH by baking soda 3 of the KH by CO2, so then my PH at 6.4 with KH at 3(from CO2) would equal over 30ppm CO2. Can you figure it this way?


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## hoppycalif (Apr 7, 2005)

The only way to add more CO2 to the water is to add more CO2 to the water. You can't do it by raising or lowering KH or by changing the pH. It is just a fortunate fact that if you have water with no other form of acid in it but carbonic acid (CO2) and no other alkaline substance except carbonate, then there is an equation that will allow you to calculate how much CO2 is in the water, knowing the KH and pH of the water. So, to get more CO2 in the water you have to add more CO2 to the water. There are no shortcuts.


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## Edward (May 25, 2004)

Salt said:


> Personally, I do 80 ppm (as calcium carbonate). I use potassium carbonate instead of sodium bicarbonate.
> 
> Also, your math is _way_ off. 1.399903 milligrams of NaHCO3 raises 1 liter by 1 ppm. Translating that to 1 dKH in 90 gallons comes to 5.10 grams. ([1.399903 mg * 3.785412 liters/gallon * 10.70109 ppm/1dKH * 90 gallons] / 1000 mg/g)


Andy485 is right, check this post for the explanation.


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## Salt (Apr 5, 2005)

Edward said:


> Andy485 is right, check this post for the explanation.


No, it's wrong. If it's right, then disprove this:

German standard is 1 dGH = 10 ppm of Calcium Oxide (CaO)

Calcium = 40.078 grams per mole
Oxygen = 15.9994 grams per mole
Carbon = 12.0107 grams per mole

CaO = 56.0774 grams per mole (40.078 + 15.9994)

10 ppm CaO = 1 dGH

71.46908 % Calcium (40.078 / 56.0774)
28.53092 % Oxygen (15.9994 / 56.0774)

1 dGH contains:

7.146908 ppm Ca (71.46908 x 10 ppm)
2.853092 ppm O (28.53092 % x 10 ppm)

Carbonate has no calcium, so we must use a standard of calcium carbonate to get degrees of hardness for carbonates

Carbon = 12.0107 grams per mole

CaCO3 = 100.0869 grams per mole (40.078 + 12.0107 + 15.9994 + 15.9994 + 15.9994)
CO3 = 60.0089 grams per mole (12.0107 + 15.9994 + 15.9994 + 15.9994)

40.04320 % Calcium (40.078 / 100.0869)
59.95680 % Carbonate (60.0089 / 100.0869)

X * .4004320 (percent of calcium in calcium carbonate) = 7.146908 ppm calcium (ppm of calcium in 1 degree)

Solve for X

X = 17.84799 ppm Calcium Carbonate in 1 dKH

17.84799 ppm * .5995680 (percent of carbonate in calcium carbonate) = 10.701084 ppm Carbonate in 1 dKH

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Sodium Bicarbonate - NaHCO3

Sodium = 22.989770 grams per mole
Hydrogen = 1.00794 grams per mole
Carbon = 12.0107 grams per mole
Oxygen = 15.9994 grams per mole
Carbonate = 60.0089 grams per mole
Sodium Bicarbonate - 84.00661 grams per mole

Carbonate:
1 / (60.0089 / 84.00661) = 1.399903 mg to raise carbonate 1 ppm in 1 liter

1.399903 mg * 3.785412 liters/gallon = 5.299210 mg to raise carbonate 1 ppm in 1 gallon

5.299210 * 10.70109 ppm CO3/1dKH = 56.707319 mg to raise carbonate 1 dKH in 1 gallon

56.707319 * 90 = 5103.658712 mg to raise carbonate 1 dKH in 90 gallons

5103.658712 / 1000 mg/g = *5.103659 g* to raise carbonate 1 dKH in 90 gallons


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## redstrat (Apr 3, 2006)

Salt you never cease to amaze me with your Chem Skills, where did you go to school?


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## Salt (Apr 5, 2005)

I have no chem skills (which is not to say I'm not a chemistry enthusiast). I took no science courses in collage (except two which were designed to pass curriculum requirements for non science majors).

What I posted above is grade school (or maybe high school at the most) level chemistry.

Get the "grams per mole" numbers from any periodic table, the rest is basic math.


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## DataGuru (Mar 11, 2005)

Once you've decided how much to raise KH, this calculator will help you figure out how much baking soda you'll need.


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## redstrat (Apr 3, 2006)

salt, the reason I say that is I have recently (last year) finished two college level chem classes, prerequisits for my Civil Engineering degree and to be honest I dont think I am as comfortable with chemistry as you seem to be, as far as calculations for concentrations, molarity, etc.... guess I just blocked all that chem stuff out after I finished the courses, never thought i would need it again or even have a use for it, lol.

anyway back to KH stuff lol.


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