banderbe

I am trying to understand precisely what 1 degree General Hardness means.

I know it is a measure of positive Ca and Mg ions, and I know it is represented as CaCO3.

What I do not understand is if there is always a fixed ratio of Ca to Mg in 1 dGH, or if 1 dGH can be made up completely of Mg, or completely of Ca.

I ask these questions in light of my results from the Aquarium Pharmaceuticals GH test kit which says I have 5 dGH, and in light of the fact that my water passes through a home water softening unit that says it exchanges Ca ions with Na ions.

I want to know if I have any Ca whatsoever in my water. If there is a fixed ratio of Ca to Mg in 1 dGH then I do have Ca and can calculate how much based on the known ratio.

If there is no ratio then I cannot know, save for a test kit, how much Ca I have in my water.

Ultimately I want to know if I need to dose Ca (and/or Mg).

Anyone who *knows* the answers to these questions, please help me out!