Usally only smooth skinned starfish are considered reef-safe such as the blue starfish (linckia laevigata) these can get to be up to 15 inches and require a minimum of 75 gallons with ample live rock to graze on. the only starfish reef safe and able to live in a Nano tank would be the orange starfish (F. monilis) or the red starfish (F. elegans) also known as "Fromia" these stay small but as with all starfish Water Quality has to be PREMIUM (exstremly high water quality) and the animial will not survive for long unless it is PROPERLY ACCLIMATED, these animals are extremely sensitive to fluctuations in water chemistry, they must adjust to new aquarium conditions VERY gradually. Hope this helps.....just my two cents.......P.S. BTW Chocolate chip's seem to be the most hardy of the starfish but are NOT Reef Safe.