Get Orange or Fighting Conchs. I have both and they're herbivores and very peaceful. They bury in sand sometimes and come out to eat. When you buy conchs, make sure they're not whelks because sometimes they can look similar. Easiest way to tell is that conchs have 'jump' forward motion instead of sliding like most snails, when they move.

Sand sifting stars will eat all life out of you sand bed so i would Not keep one.
Sand sifting star will do fine as long as there is any life left in the sand, and then it will die.
In short it is a loosing battle to keep sand bed "alive" you need critters and sifters, but after sifters are done with critters the sand is Dead.

So unless you are in the vicinity of the tropical beach and can replace live sand easily i would stay away from the sand.
Its Not an easy choice (sand looks good) but way safer and easier to go bare bottom (BB), because all sand will do is it will accumulate detritus and then it will lead to a tank crash.