I know this is a old 2 year old post, but I wanted to add some insight for the next person. I have a 480DT 540 with sump Mostly FOWLR with the exception of some (soft) corals. Zoas, GSP, pipe organ, and some mushroom that grow where they can. I currently have a 3-4yr old clown trigger 5"-6", 3yr old niger trigger 4", and similar size undulated trigger, queen angle (transitioning), passer angle (juvenile), Emperor angle (transitioning), French angle (juvenile), porcupine puffer 5"+, gem tang 5-6", purple tang 5-6", blue hippo tang 5" , powder blue tang 4-5", convict tang 4-5", blue eye kole tang 4", white tail bristletooth tang 4", 3 female one male lyertail anthias, harlequin tusk 4-5", 6 blue/green chromis, starry blenny, and neon dottyback. This is a bare bottom tank, over 1lb of live rock per gallon. If I remember right it's around 500lbs. There is a lot of caves, hiding spots, over hangs, dark spots, bright spots. I have all of those fish and I get nothing more than a quick dart from one fish to another here and there. I do feed a moderate amount of food. I consider myself an experienced reefer/fish keeper. I just wanted to offer up my experience with keeping the undulated trigger with other fish and other triggers. I also have a 120gallon sps dominant but mixed reef, with Rockflower nems, BTA, and a lot of coral of all kinds and keep a blue throat trigger in that tank. I have had no issues with the blue throat with other fish or coral.
So for any of you out there that are looking to add a "aggressive" trigger to your tank i have had great success or luck. Now with that being said my fish are not huge yet. But I've had most of them in that tank all around 3.5-4yrs. Hope that will help some of you.