My pup Rottweiler did the same thing when I upgraded to a larger tank, he would just stare and bark at it but I would pull on the scruff of his neck and tell him "no", "what are you doing" and he would just stare at me like he knew he'd done wrong. although i wouldn't recommend doing this to a fully grown rott if he has not been disciplined in that manor, whatever method it is you decide to discipline your dog, be consistent, patient, and confident.