Juvenile Smooth Trunkfish Not Eating!? HELP!

[TheFishLG]

Hey, I caught a juvenile smooth Trunkfish two weeks ago at the Destin Jetties in Florida. I caught him about 20 feet down while freediving. He is not eating anything I am trying to feed him, Frozen Mysis and Brine, live Brine shrimp, nothing, not interested. He is picking at the rocks and the walls of my 10 gallon, getting algae and copepods, but so is my mandarin. I am worried that he will die if I don't get him to eat soon. I am 13 BTW and have been keeping saltwater tanks for over three years now, I may seem like an idiot for trying to keep a Trunkfish, and yes I know they can release a poison that will kill everything. He does not looked stressed at all, my water parameters are all perfect, Salinity sg: 1.026, Temperature: 76, pH:8.4, Ammonia >o.1 ppm, Nitrates and Nitrites at zero. I have only two other fish in that tank, a Slippery D**k wrasse and a mandarin. My mandarin (named Jeffy) has lived and thrived in this ten gallon for two and a half years, even my lfs says they cant keep a mandrin that long lol. My Slippery D**k wrasse was caught the same day as the Smooth Boxfish, and he is fat every time I look at him. Thank you for any help, and sorry if this was long.