My husband and I are relatively new to the aquarium world. We have 2 Black-fin Sharks, 2 Green Severum, 1 Gold Severum and 1 Pleco. All get along well, but one of the Green Severums (the biggest one) just will not leave the Gold one alone. He/she chases the Gold one around and sort of "pecks" at it. Is there anything we can do to change his/her behavior? I feel terrible that the Gold one can't get a moment's peace.