I use filtered natural seawater thats available for free at the marine bio center on the beach and the only real complaint that I have is that you have to do almost daily water changes to reduce the alge growth. But like fishfreak said, the farther away you can get the better. I used to live in pensacola so I know how sugar fine the sand is but you might want to also think about the fish stirring it up!
Any home mortgage questions feel free to ask. Thats what I do when I'm not tending to my tank!!