+1 to thisIf you have sand you shouldn't need to vacuum your tank. If you have a shallow sandbed you can vacuum it. However if you have a DSB (Deep Sand Bed) I strongly suggest not vacuuming it. Disturbing a DSB is very bad, and can cause the tank to crash.
If you want a successful reef tank with sand, I suggest hermit crabs and nassarius snails. They keep the sand clean so you don't have to worry so much about it.
(I emphasized can, because I am sure some person will jump on and say they do it all the time with no ill affects. Sort of like bungee jumping... eventually the cord snaps.)
EDIT: Crushed coral should be vacuumed.
Bare Bottom may need to be vacuumed depending upon pump placement and waterflow.