Diet suggestions for double saddle back butterfly
 

I recently added a double saddle back butterfly to my tank. Everything seems to be going well in terms of cohesiveness with the other tank mates, but the butterfly has yet to eat anything I have fed. He does however pick at the live rocks (I got him to help keep the aptaisa population down, and he's certainly doing his part). It's been a week today, and that is all he has eaten. It's almost like he doesn't take any notice of the food, he just continues on zooming around the tank. I have a feelign he is wild caught, and just doesn't understand this food delivery stuff. He also doesn't seem to eat anythign that floats, he only picks off the rocks. Is this typical? So far he's still really active, but I can't imagine aptaisa being nutrious enough to sustain him. Although he may be getting more than that.

Any thoughts or suggestions? I have tried clam strips, silversides, prawns, krill, mysis shrimp (fresh and freeze dried), spriulina pellets, algae pellets and I even tried frozen blood worms. I've added garlic to the food a few times.