WhiteReef made some good comments. The key to them (from our clubs experience) is that live microvertebrates are necessary. So, a DEEP SAND bed is often the best thing. Add to this a healthy refugium, and algae growing in the main tank, and you are set.
Fewer fish also helps, so that their is more food for the mandarin. I guess the thing to remember is that they will slowly starve, if there are other fish to compete with. You need to have many copepods and amphipods.
Adam