mine would do that from time to time for no apparent reason. Not sure if he was spooked or just wanted to stretch out to make sure he could..
Mine would also spit water at me if i was sitting on the couch and he was hungry. There awesome fish and if i hadn't decided to go with a reef i would still have him.
Only fish i have ever seen that would flinch if you had your hand in the tank and came close to hitting him, other fish will just dart away mine would hold is ground and brace for impact.