Magnesium is a critical nutrient for humans. We need more every day because we lose it in sweat and urine. We all should take some magnesium every day.
As a chemist I know the value of water soluble forms of magnesium. Magnesium oxide and magnesium carbonate have very low solubility in water which means it's very difficult for our bodies to absorb the ions we need. My preference is for magnesium citrate which has very high solubility in water and is much easier to absorb.