I just got my regal 2 days ago. It immediately went behind some rocks and hid all day. During the daily feeding I could see him grab and food that came directly by where he was hiding. This morning when I came home from work (I'm on night shift this week) it took a few minutes to find him with my blue UV flashlight, but he had wedged himself between 2 rocks under my anemone and was laying on his side. I could see his gills moving, but I thought for sure he was dead. When I woke up he was swimming around the tank with my other 2 tangs, but the second I approached the tank, he swam off and hid. I read that this may be normal behavior, but I would almost rather see him swimming in the corner near the surface.