Well, I geuss you picked out a weak convict, my convict is so mean, he doesn't care how big, the fish are in his tank...he will kill it. When he was 4 inches, he lived with a 9 inch red devil(which now is in a 90 gal), he wopped that devil back n forth,side to side, until the devil nearly passed out.....plus the people who own jag's well let me tell you what, Jag's are territorial most of the time,the reason why you think the jag is the most aggressive, is because of it's size, so if all fish were convict size or an inch or two bigger, the CON would dominate the tank...