I just recently bought a 1.5 inch undulate trigger and an arrow crab. these are the only inhabitants of my 55 gallon tank. I have about 5 pounds of living rock and plenty of places for my fish/crab to hide. The trigger ate frozen brine shrimp shortly after I put him in the tank and then became very inquisitive of his surroundings. He found my pseudo reef and spent most of the night in there. today when I tried to feed him the same shrimp he ate last night, he wouldn't touch it. he just stayed in a small cave in the reef. I know he isn't stuck because I can see him swimming in the small amount of space he has. I am worried he won't eat so if anyone has any suggestions please reply.
Thanks in advance