Over a period of time a deep sand bed will actually become a better filtration system than your live rock. If starting out with 100 percent live sand in a full tank deep sand bed it can easily replace part or even all of a normal load of live rock. However, it is typically more expensive to put in a full (live sand) deep sand bed than to use live rock, therefore most deep sand beds are dead sand innoculated with a little live sand. I have a hard time considering bagged, shelf stored, sand as live sand. A shallow sand bed will never out perform live rock. A sand bed should be less than an inch deep or over 6 inches deep to be both safe and or beneficial. If you want cosmetics go for an inch. If you want animals and wrasses go for 3 to 4 inches. If your major concern is biological filtration go for 5 to 6 inches deep (this is a deep sand bed).