HCA: Hermit Crab Association

I came across this tutorial for a natural-looking vivarium, and am curious if the materials used in this process are safe? Would this make for a good environment for them, or would they just tear up the foam stuff? Thanks!
https://www.youtube.com/watch?v=iLDN9V3e3CY

**edited to add- I wouldn't plan use it on the entire tank, just the short sides where there is no UTH, assuming it's safe for them!

Anything soft and spongey they will pick at. The false background that are made with silicon covered foam and then topped with cocofiber or peat will stand up to them, to a point. Foam by itself will get torn apart and possibly eaten.