Do you have any other tanks (like a 10 gal)or you could use a divider until the other gets larger ??? 8)There are fish thant are called target fish
THey usually use these kinds of fish in African cichlid tank......to bring down agression between' most fish like the larger Angel you have would probally be less aggressive to the other
But, make sure that the "target fish" are fast enough to escape
A good example would be Pencil fish
One more thing make Lot and Lots of hiding places ;D