Nothin' but sand! So many people say it won't work, but I've always used sand in my 5 tanks and I haven't ever had an issue with anaerobic pockets and my plants grow amazingly well. I keep the substrate a maximum depth of 2-3" toward the back of the tank and 1-2" at the front.
I live in Norfolk, but I grew up in Ashburn :-)
I've always been tempted to try sand. I like the look of it. I'm thinking of putting sand in the front of the tank and pushing the flourite to the back. That way I can see if glosso and Blyxa Japonica will grow in it successfully.
Near the ocean, I envy you.