Some Nice Extras for Your Crabitat

1. Cholla wood.  Crabs love to climb, and cholla wood gives them somewhere to do it.  It's extra fun for them if you can find a piece that has a large enough hollow middle that they can climb into it like a tunnel.  The crabs also love to eat little pieces off the wood.  

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2. Sideways cup, or other sort of hideaway.

3. As mentioned in the humidity post, a moss pit or bubble pool.