Chemistry Forum

My tap water is fairly high in carbonate hardness (KH), and I'm diluting it with a fertilizer containing phosphorus pentoxide. I have a couple of questions:

1. When P₄O₁₀ reacts with CaCO₃ and MgCO₃ in tap water, what are the products?
2. Are the Ca and Mg products water-soluble?

Calcium and Magnesium phosphates will be produceds. These are not soluble in water.
The Fertilizer contain also Phosphates as Ammonium or potassium salt. There is no pure P₄O₁₀ in the fertiliser.