2.5" is not deep enough to get the benefits that come with a DSB. It is probably just trapping detritus. Nassarius and conchs are good sand stirrers. They will likely not be able to keep up. If your are curious, take a gravel vacuum and poke it down in once or twice, see how much junk you suck up. If you decide to clean it going forward, just start by doing small sections at a time.