I don't know how much you've looked into this fish.
Sometimes, they'll eat Aiptasia in captivity, but far more often, will not eat at all. Of the ones that do eat in captivity, their preferred diet consists of worms, lots of different worms from feather dusters to coco worms, etc. When they eat, they often like clams, too.
Some people have been lucky with them, but most are not.