This is a starfish. They don't need you to feed them because they eat things floating naturally in their fish tank. He won't hurt you if you try to touch him.
Starfish can grow to be a half inch, to a couple of feet in diameter.
Information shared by Dallas North Aquarium. Graphic courtesy of Ken Knezick. This Research Module may be used by teachers and school districts for students, but may not be Whacked or republished on any Web site or in any other electronic format without express permission. All other uses, transmissions and duplications are prohibited unless permission is granted expressly.