HCA: Hermit Crab Association

I’m still new to this website and wasn’t sure where I should post this question since I didn’t see a topic for “Substrate.”
I’ve had my 3 hermit crabs for almost a month now and they still seem like they are stressed. One has been hidden under a bowl for two weeks (I don’t disturb him) and the other 2 only come out around 1am (I sat up last night and waited for them ) The rest of the time they are hiding under their coconut.
It was suggested that I add oyster shells and worm castings to the top of their substrate (coconut fiber & play sand combo) since I have one that is under right now. I was just wondering if this is recommended?
I ordered them organic food from one of the websites and it came yesterday. I also keep their tank at the correct temperature.
Any suggestions would be greatly appreciated or maybe I’m just worrying to much. Thank you!

Those suggestions are good. Are you monitoring the humidity as well? Do you use dechlorinated fresh water and dechlorinated salt water? I recommend Prime dechlorinator and instant ocean for the salt. Plus, check out all the care guides on this site. The more information you have, the better the crabbies will be.

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How deep is your substrate? The general rule is a minimum of three times deeper than your largest crab, or 6 inches. It should be mixed with dechlorinated fresh or saltwater to sand castle consistency. Dry sand won't let your crabs dig and molt.

I'm not sure if I would put the worm poop directly on the substrate. Since it is organic due to the high humidity it can potentially start to breakdown and cause issues later. A plastic peanut butter lid or similar works great for a makeshift food bowl.

The oyster shells would be fine to put on the substrate too. I like having a calcium pit in my tanks. That way it's easy to monitor and change or add fresh.

I have a 20 G tank with three rescued crabs in. They have been in it since late last year and very rarely see them. When they do see me they usually run for the hills.