Question
When you talk about mineral content in the water are you talking about the hardness of the water ie the calcium and magnesium?

Answer
Water hardness, however, is a general term referring to all the minerals in water - calcium, magnesium, iron, and heavy metals.  However, water bureaus will publish this information separately because they are most interested in calcium, which can damage pipes.

If you use a home test that only checks for calcium, this will be sufficient since calcium is usually the most abundant mineral found in drinking water.  Otherwise, a meter checking for Total Dissolved Solutes (TDS) will be more encompassing.  

Good growing!
Jacob Farin