Starfish come in many varieties, are fascinating, and depending on the variety can serve a utility type purpose in the marine aquarium. Some starfish can help clean-up the aquarium by eating food missed by fish. While others like some Brittle stars are useful in that they can get to and remove dead fish that can't be removed by the aquarist. The hardieness of starfish range greatly depending on the variety. Brittle stars are hardy and easy to keep while Linkia starfish are much harder to keep long term in the marine aquarium.