Definitely a crowded tank, but that wasn't what you asked about.
Brittle stars, or even better Serpent stars would do fine, as they take the same food as fish.
They're also very active when food is in the water. Some people find it fascinating, others find it 'creepy'.
Fromia or Linkia stars are beautiful but can be very hard to keep long term even in larger tanks.
Their dietary requirements are tricky and not well known. You'd need to have the right biofilm on rocks and other surfaces.
They're also very sensitive to water chemistry/quality changes. So if your system isn't very stable, they won't last long.
Also Fromias in particular are sensitive to transport and require a very long acclimation.
Nonetheless they are really exquisite.
Chocolate Chip stars and other
Protoreaster species aren't reef safe because they will eat corals, snails, clams, other starfish, etc.
However I have not heard that they attack anemones. I'd be interested in hearing if anyone knows for sure on this.
Asterinas are hitchhikers, they multiple like rabbits, and aren't particularly attractive. 'Nuisance starfish', basically.
Although they're generally reef safe, some species will reportedly attack corals, particularly zoas.
