I think you'll be hard pressed to find any sea stars of the Asteroid family (basically thick bodied, symmetrical webbed look.. ie that "traditional" looking starfish) that are reef safe. Most of them out there are predators and will eat quite a bit.
If you must stick a starfish in your tank with those of the Linckia genus or a variety of serpent or brittle star (stay away from the green ones!)
Linkia - Fromia = reef safe but not easy for beginners to keep long term.
The best ones are the little guys that come on your live rock and multipy like crazy. 8) Even noobs like my cousin who can't be bothered to do a water change can't kill them. I'm drawing a blank on the genus right now...Asternid or something like that.