If, say, a tank was filled with dechlorinated tap, would it be reef safe eventually after enough partial changes with RO?
My 75g tank (which fits this description) is FOWLR but I've not eliminated the possibility of going reef down the road. My water is well water, run through a whole-house filter system, which I dechlorinate before use even though my water test from when I had the well drilled didn't show anything other than normal minerals when I had it tested... a touch high on iron, IIRC.