HCA: Hermit Crab Association

i use EE and it has some mold. I am planning on switching to half EE half sand, when i get a bigger tank, whenever my crabs decide to come out.
It smells like a fish tank. When i fix their food, i leave the top off to let it air out. Is this normal?
I know they are not dead because one changed holes, and the other has a tunnel looking thing(viewed from top) and the shell that was covering it is moved.
I found a thread on this, but i can't find it today.

You may have a water leak from one of your ponds/dishes. I use part EE and if it gets too wet, it will start smelling badly. You really need to keep an eye on the moisture.
The normal smell of EE is a woodsy/earthy type of smell.

You may also have a case of crabs hoarding/inadvertently hiding food, especially protein-based stuff, in which even a tiny portion (or several tiny, hard to see portions scattered somewhere) can create a mini-stink.

It's gotten to the point where I nearly got used to it on mine, as long as it is relatively slight and doesn't cause a dreaded dark-gray bacterial spread in my mostly-sand substrate (in which case calls for a major deep clean).

i had a tank with Damp EE in case i needed more setting for about 6 month, i found it to rot and stink.. It was biodegrading. I know others seem to think that it wont do that but my opinion from my experience is that it does. The deeper i want the more it stunk. It wasnt even wet any more just damp at the very bottom..