When the bedding and vermicompost become vermiCASTINGS, there will be absolutely nothing harmful to crabs....hermits or otherwise.

Anything passing thru a worms' digestive tract is magically de-contaminated of all from our polluted world.

Also, that stuff (newspaper colored inks are safe now, but avoid stickers and labels ink dyes on cardboard) ain't gonna hurt those crabs* anyway if it doesn't harm the worms. And it doesn't.

*That said, I don't know squat about crabs except if you've got 'em don't let anyone know.

Chuckiebtoo

Ok thanks. I did some additional reading since I posted and I think I'm going to stay away from newspaper/newsprint just to be safe and use left over cardboard paper towels rolls and toilet paper rolls as well as things like egg cartons when available.

Next question: Hermit crabs are sensitive to things like coffee. As long as they worms completely process the grounds there shouldn't be an issue but if there are some left over bits in their castings that are unprocessed this could potentially be unhealthy for the crabs. What is the risk of leftover unprocessed bits ending up in the castings and what is the best way to ensure that the compost is fully processed into castings so I can eliminate this potential risk but still use worm "favorites" in my farm.

There will be definatelly coffee grounds left, they are just too hard for bacteria and worms to process. Have a different worm bin with coffee grounds for your plants and another one for your crabs. As for paper, who knows what's in it. Try and see. Another source of paper bedding - brown grocery bags (without ink and glue, to be safer). It looks like you need to try different things and small separate bins might help.

Different worm bins for different purposes is the way to go. I have 7 different composting systems -- a modified rubbermaid for food scraps indoors, a worm factory for food scraps outdoors, a small decorative wooden worm box on the deck for garden clippings, an Earth Machine for chicken manure, a pile for horse manure, and a large wooden box to make food for my worms. Photos on my website if you're interested.

Anyhow it sounds complicated but is actually quite easy since you just place the bin near the place you would use it!

Here is a link that might be useful: my compost bins

Will dry hay, straw, or grass work as a replacement for the paper layer(s)? Those things are all hermit crab safe as long as they haven't been exposed to a lot of chemicals/pesticides. Or do those materials still need to be used in conjunction with paper?

I often use hay or straw, and never use shredded paper. Any high-carbon "brown" will work fine.
Hope this helps. Good luck, Pete

No idea of the sensitivity of hermit crabs to chemicals. But almost anything pre-composted and then vermicomposted should be pretty neutral. i actually think cardboard might be less of an issue than hay, for example, at least if the hay is 'fresh' - hay could have lots of natural toxins. Straw should be pretty neutral. Experiment and let us know.