No RODI means copper, brass stopcock in your house or even worse copper piping will introduce copper. Cast iron pump impellers at your suppliers pump station could be repaired with brass/bronze welds, etc.Salinity is 1.025
Reef Crystals is all they had at my LFS when I started so it’s what I went with
Unfortunately no RODI water but I use declorinator and test the water for chlorine and ammonia before using any water.
Yes I am using API test kits except for magnesium which is Salifert
RODI is cheaper than many coral frags, why skimp on it ?