HCA: Hermit Crab Association

Hello,
A couple of general questions about the substrate. I have the play sand and eco earth mixture. My humidity has been between 76-80% about 3-4inches deep. Is there ever a need to moisten the substrate? Also, when is a good time to change up the landscape? For example I want to add in a small pool with a bubbler and exercise wheel? I have 2 crabs. Not sure if I am seeing the same crab over and over or if they rotate with hiding.

If your substrate dries out, you will need to moisten it. How fast it dries out will depend on a few factors, like how much ventilation/ air flow there is, whether your heat pads go below the level of your substrate, etc. I goog test is to poke soething like a chop stick down along the glass to the bottom - you should be able to tell if the substrate holds it's shape or collapses in, and then you aren't risking poking down onto a crab who is underground.