i have used raw sea salt with local marine FOWLR, 15000ltr as it was cheapest option
only prob was phosphates, they clean it as best they can
wouldn't use it on a reef tank though
in the extraction process it loses some of the trace elements
sorry can't help, but could show you the place where my tanks are now
or point you in the right direction
there is a couple of streams in town that may still be good