HARLEQIUN SHRIMP ARE THE ANSWER. I am babysitting Boret's harley right now... you can hand him asterina and watch him eat them right in front of you. I have yet to see one die in captivity as long as you have stars. When your stars are gone, put him on Wamas and someone will jump on it right away.
Also, they are just about the coolest looking creature you can get for your tank.