hello!
I love your fish!! very beautiful!!
About the hermits, Calcinus elegans is fine, a bit bully, but not dangerous to keep (except for the snails). But the two others (Dardanus gender) are carnivorous predators, and they can attack and eat small fishes and animals in the tank... Better not have gobies in your tanks!
Not to mention they get really really big, lately, I saw one of these larger than my hand...