These extraordinary looking animals also have an unusual appetite. They eat only starfish, and nothing else. There are some scattered reports of them taking other tube-footed echinoderms, such as short-spined sea urchins, and some people have reported being able to feed them frozen starfish, but for the most part, if you get one, be prepared to give them an expensive diet--live blue linckia starfish.
I keep feeder linckias in the sump of my 60gal tank and put them in with the harlequins, which are in the 10gal seahorse nano. I have a pair of small harlequins which I've named Boris and Natasha (bluer legged one is the male, they only live in mated pairs), and they get one feeder linckia every 1-2 months or so. They are shown above going to town on the poor starfish. It's a cruel, cruel world. They pin the starfish upside-down in a corner and literally eat it alive for many weeks (tube feet first).
They'll even drop food such as shrimp that I feed the fish in that tank in the starfish's mouth to keep it alive (food which the shrimp itself does not take!). The ironic thing is that I have several stars, including another pet blue linckia, a red linckia, and a red Fromia star which I keep very safe and out of harm, spoiled in the main tank.