For those of you with similar stock, I have a Serpent Star and several Hermit Crabs (Scarlet Reef; Red Tipped). The Serpent Star moves around the tank at his leisure, luckily for me frequently choosing to rest in the hole of a large donut shaped piece of LR
in the center of the tank, where he's easily viewed. The Hermits all gather underneath him like he's their mothership. It doesn't seem to bother him at all.
Are Serpent Stars messy eaters or something? I never see the Hermits picking on him, or eating anything underneath him - just sitting there. It doesn't seem to bother him any, and he only moves them away when one is attached to his krill and he's hungry.
On a somewhat related note, my Firefish has nipped at a couple of his "teeth" once or twice, but he hasn't jerked away, and instead shares the Firefish's bolt hole with him. Is the Firefish mistaking them for Copepods or something? They are a similar size and color. It doesn't seem to be trying to hurt it, and if it is, it's certainly not very effective - the star still has all its limbs and teeth, and doesn't seem particularly interested in running away.