I currently have a huge Black Nasty (about 14 or 15 inches) housed in a 270 with a big Jag (about 12 inches) and a Green Terror that is about 8 inches. The Nasty runs the show....no doubt. But he also is still a model of health. So far so good. Oddly enough he seems completely indifferent to the Jag. He shows some aggressiveness to the Green Terror who is standing his ground but there have not been any real conflicts. The Tank looks great with the big Cichlids in it.