I would say Sargassum is the best option, someone mentioned digging in the sand, I have never seen my Sargassum at the bottom of the tank. He is a very hungry fish though, I certainly wouldn't put it past him to eat a shrimp if you tried to add one.
Keep in mind we see all the "my Pinktail has been in 6 months with no problem" posts....Success with Triggers is measured in years, not months....They change substantially from juvi to adult.
I will also add that I see Crosshatch mentioned a lot as reefsafe, the problem with Crosshatch is they are not available at small sizes, you simply can't get a male under 6 or 7 inches. I've had my 7.5 inch male (w/ female) about a month, and this fish is in no way shy, my tank is full of "aggressive" fish, and he has a mean streak in him that the other fish know not to mess with.
No matter what type, a big Trigger can be a mean Trigger. Reefsafe, maybe, but "community safe" may be another story.