Lions are not reef safe because they will eat shrimp. Hermits and snails are absolutely safe. I have never seen a lion even attempt to eat a hermit or snail. Feather dusters, and even crabs should not be a problem. Lionfish are a little dangerous towards small fish, so if you do not have shrimp or small fish (pseudos, dottybacks, tiny gobies, etc.) in your reef, they would not be a problem.