The title explains my problem pretty well but here is some back story to it; I have a 50 gallon tank. In this tank I had a bunch of Sliverdollars, a eartheater Cichlid, three Angelfish, and two Blue Gouramis. Since then my Eartheater had died and I have moved out my Angelfish. Now one of my Gouamis being aggressive and chasing my other Gourami around until the point she was very stressed out and wouldn't leave the bottom of the tank. Noticing this, I decided to temporarily move her with my Angelfish. Since then my Gourami has been relived of the stress and I assumed that my one Gourami was chasing her because she was smaller than him, but after this he started to chase my Sliverdollars around. I'm starting to fear he will stress out my Sliverdollars until they die. Plus, I will have to move my one Gourami out of the Angelfish tank and put her with the other Gourami because when the Angelfish get older they will become more territorial against the smaller Gourami. I'm pretty sure my one Gourami that is chasing my other fish around is a male, while my other one seems to be female. Is there any way to stop my Gourami from being so aggressive?