Tonight, I came home and checked on my tank. My hippo tang was "asleep" in it's usual nighttime hiding spot. However, I was startled to see my three-stripe damsel snug against the tail of the hippo, also "asleep". I thought that one of the fish must be dead, but they were both fluttering their fins and healthy looking. Over the next twenty minutes or so, the damsel moved further up alongside the hippo and was actually "snuggled" under the hippo's pectoral fin. Kind of like the hippo was holding the damsel. Both fish have been perfectly healthy as of late but I've never seen behavior like that before. They looked to both be very content. They typically do get along pretty well. It was actually pretty charming. Too bad I don't have a digital camera. Is this fairly normal? Has anyone else seen this before?