I have a butt-ugly 15 year old puffer fish with anger problems?

So we got a 75-gallon saltwater fish tank with a yellow spotted puffer and a powder blue tang. (I love the tang!) It's not that I don't love the puffer, too, but he's really ugly and I think he may have anger problems (haha it's a joke, realists.) He presses his teeth against the glass and tries to bite and he follows us around and he is always slamming into the sides of the tank. Today I was just walking by and he swam at me so furiously he splashed water out of the back of the tank and onto the floor. Is this natural behavior? We just fed him, by the way!