Ohgezz I wish it was as easy as adding salt LOL. Marine use rocks as filters and use a protein skimmer. You can expect a marine tank to burn a small hole in your wallet. Your also better buying your salt water from LFS to avoid some bad stuff, it's not easy
I've been thinking about a marine set up recently. From what a few people have told me, it's not as difficult as some people like to make out BUT it does require a lot of research. I'll probably go for it at some point once I have time to properly research