Snails that dig their way deep in gravel or sand must be checked often since a dead buried one may be overlooked and will cause colapse when it starts decomposing.
Keeping such deep layer of sand is not good. If posible, try ta take out some,vaccum the surface regularly and stir it once in a while to let small amounts of gas leave to the surface.
With sand, deep vaccuming is not really necesary since the debris will not penetrate it, but stay on top. Keepin a regular cleaning routine will keep you out of trouble.