First and foremost, a 55 gal
is way too small for this species. It needs something along the lines of an 8 ft tank to do even remotely well long term. Please be sure you make some future plans (soon) to upgrade to it's needs.
As far as sleeping habits, this species tends to hide in caves, crevaces and the like as apposed to burying itself like it's cousins. If your rock work is more closely confined and no real area's for the wrasse to bed down, I would create a few. Just watch for dead water flow spots in the process. The caves and such will help reduce the wrasses stress overall and increase it's prosperity. They love to dart in and around things (including caves) and are increadibley active.