Lots of folks who keep expensive corals (SPS sticks) don't like to use the faucet water because supposedly the water quality is not reliable and the natural viruses and bacteria and what not have been suspects in tank crashes with Scripps water. Perfect for fish, ime, but the rumored consensus is that salt from a box/bag is more consistent with non-hazardous RODI/salt providing stability vs the unknown contents in NSW that is downstream of the San Diego Muni outfall and the TJ River, both sources of potential problems not to mention the impacts of storm runoff. People also notice that the NSW tends to be tinted green from the planktonic component that thrives in our temperate ocean.