Am i right about this calculation?

[Patrice]

If i calculate they calcium and my Gh, I can get the results of the magnesium with out mg test kit. is this right?

This is for my freshwater aquarium, but no one is giving me a respond so maybe someone can help me here because the principle should be the same for salt water.

I have 17 ppm of calcium
and 100 ppm of GH (5)

logic dictate, i have maybe 83 ppm of magnesium

100 - 17 = 83 ppm magnesium

 

[carey]

You can GUESS at your mag based on the other two but no way to know for sure unless you test. My mag runs about 3X my calcium level which is right where it should be in SW. I do test also though to make sure it doesnt drop.

Hope that was somewhat helpful.

 

[ccCapt]

No. They are not related in that the value of one or the other (calcium or alk) will influence the value of the magnesium. For example, you can add a calcium or alk supplement which will raise ca or alk, but it won't raise or lower mag.

 

[Patrice]

Thank you all for they answer.