HCA: Hermit Crab Association

I've been a crab owner since December, 2016. I love them and want to make sure there is plenty for these dudes to do! I have a 20 gallon tank, and it's long not wide. I want to know if they prefer having climbing things than crawling space. I see lots of tanks where there's very little crawling room...

Not really. I've had one since late December, and I adopted the other about a month after that.

My crabs are both buried in the substrate. They have been buried for a long while, but I checked on them a day or so ago and they're both alive and well. It doesn't smell like rotting fish, either. I don't believe they're molting, because neither had molting coloring. Am I doing something? I've cont...