My guy is active at all times.
30 minutes in the tank, he was already eating and being territorial with the Morays. They were getting too close, for his liking and he was taking swipes at them, with his tail.
Since then, they sleep together, hang out in the same spots, in the tank, etc.
I will say this, tho...he's eating me out of house and home. At 6" - 7", he's eating 10 - 15 pieces of krill, per day. I finally cut back and only feed him every third day, now...but, that's after he ate half a package of krill in a week.