There are many problems regarding using local NSW in reef aquariums.
The local purchased NSW comes from HMB, home to some of the most polluted beaches in the state due to agricultural runoff, cracked clay sewer lines, a healthy population of seagulls that go to the dump to eat, and then come to the beach to poo, and of course lots of boats. One of the individually most polluted beaches is known as Barbara's beach, home to Barbara's grease trap where you can get $20 fish and chips. It is about 100 yards away in the INNER harbor (there's an outer breakwall, and an inner breakwall, the inner breakwall is where all the slips are for the boats) that our NSW is collected. THERE IS NO "PIPE" going out into the ocean, they don't go out into a boat to collect it, it's all lies. The water is then trucked to a muddy lot, and run through some frankenstien filtration setup, and trucked off.
Let's pretend that the water here is pristine, when the water comes up to tropical temps it has a gravity of ~1.027-8, very low calcium, last time I tested it was ~320ppm (no joke), there's plenty of phosphate from the ag runoff due to Deniston creek that runs past over hundred acres of Brussel Sprout fields where they grow two crops a year it's non-stop. If that's not enough, during rainstorms the freswater intrusion can put a "slick" of fresh water up to a foot thick half way out to the jaws of the harbor.
Oh yeah, then there's this...
That's some pretty low Alk....
Good RO, or even good tap run through sediment and carbon is a much safer option.