What ddi you expect? You've got two aggresive fish in an 8 gallon tank that should be in nothing less than a 30 gallon, if not more. That's like putting two pitbulls in a cage together.
I have an 8 gallon nano, the damsel fish was there first and has established it little cave, I got a percula clownfish today for $10 at a local expo ( couldnt pass the oppurtunity up) I'm rehoming the damsel tuesday, but he is attacking the clownfish constamtly. How do i stop it till tuesday. I dont have a QT tank. There are planty f little caves but the clown is just swimming along the glass.