Ya there are several stars that are reef safe, the problem is getting them enough food so they don't die. Brittle stars are good because the are fast at getting the left over food, but the lankia(I don't recommend, they are next to impossible to keep in a nano), the red sea star, marbled and sand stars are usually reef safe (doesn't mean you won't get one that goes after small polyps (ie, green star polyps), but they don't chase after the food as quickly and tend to be prone to diseases.