Whether using tap or RO water, there is a benefit to aerating the water at least over night, even if there is no salt in it. Water coming out of the tap or from an RO reservoir has a different pH than water aerated for a period of time. Did a study on this subject a few years back when I had waaaaaay more time on my hands
:
http://www.lostmymarblz.com/marinere...containers.htm
I always have lots of RO water aerating in various pails or tanks for my reefs/seahorse tank. The night before a water change, I plug in the heater, add the salt and away I go.
Would never just use water out of the tap or from a non-aerated RO storage container knowing the difference in pH in our local water
