I live in the suburbs of NY. Water quality is pretty good since it comes from reservoirs upstate.
Before switching to RO, I still added Cichlid Salt to my water changes along with baking soda, and noticed a tremendous difference in coloration and overall health of my fish. Sure the water was probably mineralized, but the addition of salt was helpful.
Adding Purigen and Phosguard to top of canister finally got rid of diatoms (brown algae) that persisted well after cycling and have brought Nitrates close to zero with regular 25% water changes.
I rarely endorse, or get behind companies in any industry. However, Seachem is one of the best as far as water treatment products goes.
Now since most minerals are stripped out with RO, I remineralize the water with Cichlid Salt and buffer kh with baking soda while running UV.
My fish are thriving and the water is ridiculously clear!