My cat and my peacock cichlid do the same thing, except the cat just tries to slap the fish. My fish is not quite as aggressive as this one, but definitely is defending his home.
My cichlid has also decided he hates my bristlenose pleco. He goes to the bottom picks up some gravel and spits it in the general direction of the pleco. When the pleco runs from the rock shower the cichlid then procedes to chase after him. Fortunately my pleco is very adept at finding new hiding places once he's been spotted.