Florida Cerith snails range in size from an inch to 2''. These snails will consume diatoms, detritus, cyano, film and hair algae. They reside in the substrate especially, but will also clean the rocks and glass of your aquarium. In bare bottom aquariums they will spend most of their time on the rocks, or on the bottom glass. This species is most active at night.
They take time to "come out of their shells" and move about after placing them in your tank. Please give them at least 72 hours to start moving about. It is abnormal for them to move around right away. Additionally, when the snail is pulled into its shell, the opperculum can pull back around the corner of the circular opening. The shells are not empty, that is just how this species is.