Community tank

[White Lightning]

I have a 60 gallon tank that is home to 7 different species of gouramis, 2 red tail sharks, a bala shark, 2 small danios, a blood parrot, a convict and severum. It appears as though the blood parrot is the most aggressive of all the fish. But oddly enough it only chases the other two cichlids and leaves all of the other fish alone. Why do you suppose that is??
I know...I know... the severum will have to be moved to another tank once it gets too big. But it has not grown whatsoever in the 2-3 months that I have had him.