Sand beds are nice as they allow for more options of fish and some coral like elegances(granted you can put them on a rock, but they dont like it as much) The sand also helps trap nitrates,phosphates,etc, and the micro fauna it houses also consume it too. It justs a good cycle to have IMO. 2 to 2.5 inches is where you want to be, don't go to much deeper.
Gobys like the Diamond/Orange spot goby work wonders, i just posted how good mine is in todays daily question. He is a big one though, about 5 inches. The sand is so clean it looks new and reflects so much half my corals disppear on camera, yet you can see all the microfauna from the side view.
Then bam almost everything gone on camera, xenia, acans, most anemones,etc gone... LOL The reflection is too much for the camera. xD