Whew..good thing! Well..let's see. If you have a good depth on your sandbed you could add a cool jawfish. Bluespots are great,but average about $120.I keep a tiger jawfish..he
is really cool. If you are willing to escape-proof your tank you could get a snowflake eel or a ghost eel. You could do a small toby puffer like a valentini or a bluespotted..but they take special care, and you would have to remove the starfish.
Most of the non-reef safe fish get too large for your tank..this is the problem.
Perhaps a pinkface or paddlefin wrasse. You don't see them often.