there are several different "kinds" of that starfish, if it has color, chances are that it will be a pest. if its all white, then i would leave it in. i have several white ones like yours that cause no problems, my little cousins really love watchin it move across the glass.
they will multiply quickly, yours looks like it will divide soon, and each half will regrow its arms then divide again.
if for some reason you notice damage to your corals, harliquin shrimp will eat them. just make sure to have a home for the shrimp after all your starfish are gone. IF you choose to get rid of the starfish of course.