R/o vs tap water

[fishguyxd]

I was wondering if anyone uses a product by(seachem) that "remineralizes" your R/o water. I use R/o but if i was to use tap then i would get all the extra minerals and who knows what else.

I ask this because I find some of my water tests are low IE: Magnesium is 1300 and still checking the rest.