Harlequin shrimp behavior

[Whiterabbitrage]

To battle my Zoo eating starfish, rented a couple Harlequin shrimp. Are they nocturnal? They don't move much... Not at all in fact. They only eat if I hand them a starfish. They don't actively hunt. Is this normal?

 

[Calappidae]

They hunt when hungery. Actually that should be used as an indicator when they need fed again as they'll hide with their little starfish friend for weeks (or hours for asterina's case).

Pretty but hardly ever seen.

 

[Whiterabbitrage]

Thank you!