I just purchased a 55 galloon tank from Walmart filled the tank up with water, added the chemicals to make the water safe for the fish. I purchased 2 bala sharks, and 3 silver dollar fish. A few days later I purchased 2 Silver Angel Fish and i notice today that one of the Angel fish is going around the tank and it nibbles on the bala sharks tail, and also it nibbles on the sucker fish. The fish in the tank appear to be bothered by this activity. I read on a site that says if you have 2 Angel fish in the tank that one can get dominate and agitate the other fish in the tank. Should I be worried about this behavior or is it alright if the Angel fish does this from time to time? Any advice would be appreciated.