Starfish in reef tank?

I have a 120 gal tank that I have been starting to add livestock too. I want to have a chocolate chip starfish in it but I also want to have coral. I know that the starfish are not reef safe, but I wanted to know if it would be ok if I made a platform about 5 inches away from the sides of the tank and have in hang from the top of the fish tank with string. If I did this would I be able to keep coral on the platform? Any advice will help.

Thanks