It depends. I buy seawater from my LFS that has been purified so I don't have to worry about pollutants. If you're going to gather it yourself, I wouldn't. RO water and a salt mix would be better.
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12g Nanoreef. Zooanthids, Ricordia, Star Polyps, Acans and two clownfish. CF Lighting, 75% actinic blue, 25% 10,000k white.