Starfish.

[muck]

Definately stay away from a linkia in a tank that small.
If you really want to try a star I would only go with a Fromia milleporella.

http://www.liveaquaria.com/product/p...cfm?pCatId=578

I had 2 of them in my 40 for quite awhile and they were doing great until I treated my tank with interceptor (for red bugs). I didn't realize they would be affected as in none of the research I had done they were never mentioned as inverts being affected by the treatment.