It is a yellow margin trigger, they are mean and not reef safe, related to the titan trigger. It is dumb to buy triggers in a rock filled tank, they grow fast and will occasionally snap, then you can't catch them because they are so stealthy. You end up taking all rock out. I can see this is a reef making you in even more of a difficult situation. Sorry to be so blunt, I just feel bad for the situation your in. I bought a small niger once and it killed my favorite fish an xlarge tasseled file, I had to take all the 100 lbs of lr out and it was a fowlr so I can only imagine the hassle if it was a reef.