question on water softener and soil

hi bros,

so i read the contents of a gex soil and it says to contain iron oxide.
then i read the functions of a water softener ( be it from any brand) and it says to be absorbent of heavy metals, iron included.

so is it advisable to mix these 2 together? In the end of the day, what i really want, is a planted tank and soft water.

thanks in advance for all advice