May be this will work for a starfish - it worked for cucumber:
My golden sand-sifting cucumber (was mistaken for filter-feeders kind) in 5g received supplemental feeding for a couple of months - the sinking shrimp pellets. Then united 2 tanks in one 20g tank.
Drop one not far from it's head, and check the next day. If not eaten - remove by pipette or rigid air tubing. It may take a few days.
Tank received also frozen mysis, but I had never seen cucumber eating this, only bristle worms.