as far as aggression goes i do have some experience. i have a 150gal with a huma huma trigger, bursar trigger, clown trigger, small lion, all of which are 4-6inches, 19inch snowflake, puffer, yellow eye tang, coral beauty, and three of the most aggressive yellow tail damsels. i have no problems, but one suggestion is have lots of rock and caves for the fish to get into. i did have a niger trigger, but he was beaten up by the huma and the snowflake eel ate him. a 150gal tank is not that much more expensive, and it will pay off in the long run when it comes to your lives stock. just like anything else, bigger is often better. good luck!