okay.. get this.. my biggest of my two yellowtail is about 1 or 1 n half inches.. i've seen him fend off my 2 n half inch maroon clown!! maroon clown? they're suppose to be aggressive, too.. i want to take it out, but it's for someone in this family that enjoys it's coloration.. the small one is okay though, i know it may have problem in the future.. oh yeah, as for aggressive fishes, my tang is really agressive for some reason.. i mean he would be okay so long as no one starts trouble with each other... if lets say my clownfish and my damself fish starts bickering then the yellow tang jumps in.. it's weird, from my viewpoint it looks like he is a fight preventer...