They should have sand for them to hide in or sleep. If you have a bare bottom tank you can always add a small tray of sand to give them a place to hide and sleep. I have done this in my large bare bottom tank by adding a small tray for sand for my clouded wrasse. It took him a while to find it but once he did it dove into the sand right away to sleep for the night. I plan to add a larger tray that will be removable in the future so I can periodically clean the sand in the tray while also accommodating more than one wrasse.
They had one at my LFS for sale a while back. He/She was awesome looking, it was about 3" long. They did say that they get quite large, loose their color(ie the juveniles are much more pretty) and can get quite nasty. Just food for thought.