HCA: Hermit Crab Association

I'm making a list of the supplies I'll need to make a background for the new tank |I'm gonna set up. I've seen some pretty cool DIY projects with spray foam and silicone etc but What is everyone spraying the foam onto? Plexiglass, wood, screen of some sort? Also , the silicone is usually mixed with the EE or just slapped on top before its dry? I've seen some use grout but does the grout chip off? what kind of grout and can I mix or place EE on that? Would the grout be stronger than the silicone and less likely to get destroyed?

There are so few of us doing projects like this, that I would really recommend you check out a terrarium forum like Dendroboard. They're frog-based, but so many of their members have done projects like this they would be able to offer much more help!

I can only say what I've done - I used styrofoam panels and pieces and glue to create a base structure, and then covered that with great stuff. On top of that I smeared a mixture of concrete binder and cocofiber, but it doesn't hold up to humidity or water and will start to melt again if it gets wet. Water also gets between the styrofoam and the glass and gets funky. I did another project where I did the great foam straight against the glass and used elm bark to cover the surface and that one worked out much much better. One project was for a frog and the other was for exotic roaches.

The problem with crabs is that they pick at things! Anything soft or squishy will get pinched off and eaten. You have to keep that in mind when building so that they don't accidentally poison themselves. Most of spray foam and cocofiber backgrounds are not made to be used with clawed animals.

Definitely check out some terrarium/vivarium forums. They have a lot of cool ideas! But like Wode said, I would recommend staying away from foam products though, based on experience with a waterfall I made. A background might not be as bad, but my crabs crawl all over the waterfall and even though I sealed it, they have poked holes through that and started to pick away the foam. All my hard work ruined! I covered it in a concrete mix, siliconed river rocks to it, and sealed it in silicone. I let it soak in a bucket of RO water for a week before putting it in the tank.