Hey pj86,
the emperor shrimp is doing fantastic! He lives on a duncan coral which has a single stalk and 20 or so heads. The duncan is attached to a small rock which forms a flat base with an irregular surface. The emperor never leaves the stalk of the duncan. He just circles around and around all day. I do not believe he has touched the sand bed since I got him two months ago.
Every morning and evening I turn off the circulation and squirt a variety of foods at him with a turkey baster. He recognizes the baster as the source of his food, and starts vigorously waving his arms around. I must say that my shrimp is a terrible hunter. There can be food piled at the base of his coral, but he often doesn't recognize it, and waves his pincers right across it. You would think he was blind. However, if I lightly blow the food up at him, it will stimulate him to eat.
Right now, I feed him a large variety of foods. He gets frozen mysis, Hikari marine S pellets, frozen cyclops, shaved bits of raw shrimp and whatever meaty frozen food cubes I have on hand. Again, since this is normally an animal that hunts from the back of a cucumber, he will not leave the host animal to hunt, so you have to be certain that food comes to him. It is imperative that the host be a bit slimy, like a coral, cuke or nudibranch, so that the slime can trap small bits of food for the shrimp to eat.
I think he is the most fantastic thing ever, but I really like the smallest, most passive animals. I think a dedicated tank is almost a must. Mine is in a tank with 6 sexy shrimp, a read headed goby, a peppermint shrimp and a pom pom crab. The peppermint and pom pom crab are nocturnal, so they don't compete for food at all, and the sexy shrimp are easy to distract with a pile of food pellets. If your shrimp were to have to compete for food at all, he will starve. Also, I think I got very lucky in that mine is happy on his duncan, as finding a suitable host is a challenge.
What is the shrimp at your LFS living on?