# mg/l to degree conversion



## lakerat37 (Aug 4, 2005)

is this the correct formula to convert mg/l to degrees of KH or GH?

mg/l divided by 17.8 = degrees of KH or GH


I am trying to figure out the CO2 saturation in my planted tank.

My KH is 60 mg/l and the PH is 7.4 I really do not think I have enough injected CO2.

The GH is 80 mg/l (slightly soft?)


Thankx, lakerat37


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## Salt (Apr 5, 2005)

"Degree" is a German measurement based on the measurement of calcium in calcium oxide. One degree equals an equivalent of 10 ppm of calcium oxide.

Based on atomic weights, 10 ppm of calcium oxide is 7.15 ppm of calcium and 2.85 ppm of oxygen.

To carry this over to calcium carbonate so that you also get 7.15 ppm of calcium, you need 17.86 ppm of calcium carbonate. This contains 7.15 ppm of calcium and 10.71 ppm of carbonate.

In order to convert correctly, you need to know which standard your test kit is measuring. If its ppm reading is equivalent to calcium carbonate, then dividing its result by 17.86 will yield degrees of hardness. If its ppm reading is equivalent to calcium oxide, then dividing its result by 10 will yield degrees of hardness.


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## Laith (Sep 4, 2004)

No, you definitely don't have enough CO2...

60mg/l of KH divided by 17.86 gives you a KH of 3.4. At a pH of 7.4, you get a CO2 level of 4mg/l which is basically what you would have with *no* CO2 injection.

If the reading is given in equivalence to Calcium Oxide (which test kits do this by the way... never heard of it) you'd have a KH of 6. This give you CO2 at 7mg/l; still way too low.

I'd say you have an issue with the way you diffuse your CO2 into your tank...


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## JaySilverman (Jun 19, 2005)

mg/l = ppm

You currently have like 4 ppm of co2 in your tank. Add more co2 till you get your PH down to 6.5

With a KH of 60 ppm and a PH of 6.5 you would have at least 30 ppm of CO2 which is where you want to be.


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## lakerat37 (Aug 4, 2005)

Thankx guys! This helps alot...time to crank up the bubble counter.

lakerat37


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