HCA: Hermit Crab Association

Heya!
I'm back and as a quick update my hermits had their first molt with me and it was a success!
anyways I noticed in my crab tank that they lacked much to do to keep themselves entertained
So do you have any ideas on what I could buy in order for them to have fun?

Yay for a successful molt!
Try a hamster wheel if you can fit it! Either a saucer type or a vertical type will work, and the crabbies love them.