David
Have you had any experience with Fighting Conches(Strombus alatus)? I think they are more suitable to contemplate than the Queen or the Crown.
This is info that I have on them:
"The Fighting Conch is an excellent sand sifter for DSB tanks. It doesn't grow as fast as the Queen Conch, but each one needs 2' x 2' of surface area to get enough to eat. On occasion it will bury itself completely in the sand to where one eye stalk is all you can see, and may not resurface for two weeks. This is normal, and perhaps that is its growing period. They jump quite high with a very powerful foot. The snout extends across sand and glass, but never on the rockwork, taking up detritus from the sandbed like a little vaccuum cleaner. The foot helps it to burrow in the sand, as it often does, and also can shoot this little mollusc quickly to another spot when it feels threatened. This "jumping" behavior is what gave them the "fighting" part of their nickname, as they are actually peaceful scavengers that will not harm things in the reef. It does also have a hidden spine, but this is used only in defense; it has not bothered any of the inquisitive fish in my tank."