For evaporation, the salt says in the tank water so when you top off the tank you only add fresh water. I was on a well system here about 10 years ago and the water was not that good. I would suggest using RO
, either from you own system, a LFS
or at least from a water dispenser station like outside of some Wal-Marts.
's run their salinity low for several reasons, one is to save $ on salt. Natural sea water is higher than that, I run mine at 1.025-26.
As for the Coral, I will let others guide you as I am nowhere's close to an expert but I have read posts that discourage it's use...