Right NOW I'd say Zonatus, but that's because one of our Zonatus just killed a male Breidohri in my son's 75 Gallon the other night. The Breidohri was the top dog in the tank, I was worried about him beating up the Zonatus, but one night the Zonatus suddenly learned how to fight back. They were both 6 inches, and I thought a little too young/small for serious damage like that.