Move quietly, and feed a little flake that will waft about the tank, then sit back a distance. They start out shy, then, if they find no predators or frightening things, they become full of swagger and come out to watch you. Mine disappeared when I added a rabbitfish to the tank [large] and I thought he was dead. When I finally took the rabbit back to the lfs, about a week went by and then back came our yellow watchman. He bosses everybody on my list, occasionally nips a tail, but nothing serious.