Zebra hermits aka left handed hermits (Calcinus laevimanus
) lose their "zebra" appearance as they get larger. Does the left claw look much larger than the other?
As far as your set up is concerned if just keeping these guys, the basics will do. You don't necessarily need LR
as they are negligable on the bioload. I would however suggest a few small pieces if you can get some cheap. It will give them something to pick at naturally and add to you viewing pleasure overall, but again not absolutely necessary.
When feeding, keep it light and sparse. A few times a week is fine and use sinking type pellets so the food is not wasted and the crabs can access it immediately before it deteriorates.