I have a Sargassum Trigger in my tank now. So far, so good. I've read that they are "reef safe" from different sources as well. He's only been in for a little over a week, and he hasn't touched any corals, shrooms, Xenia, etc.
Another thing to consider is the heavy bio load of a trigger. They eat and crap a lot. I hadn't had a trigger in a few years and forgot how much they eat compared to tangs and other "reef" fish.