My money is on the peacock. The 2 peacocks I own are constantly out and about turning over rubble, coming to the front of the tank when I sit down, reconstructing their burrows. They never seem to be satisfied with the structure and it's real funny to watch them be so picky. I scatter around loads of rubble which seems to make them happy with options to build with. Kinda like my own personal automatic underwater lego set!:lol: