I had a 75 gallon frag tank, and it started really nice... but I ended up with a lot of cyano and algae growth in there. I'd recommend a bit of flow and stay on top of the maintenance of the tank. Maximize your space as well. I like the way that Rob has his frag tank set up.

I've seen some really nice frag tanks up north in MD. They had a ladder styled frag racks that stretched from the bottom to near the top... but it left a lot of space beneath the racks, and that's the problem that I had when I attempted to recreate the idea.