When Crabs molt, their new exoskeleton (shell) is soft and they are vulnerable. Instinctively, they hide out. I had that happen a couple times in my tanks and, at the beginning, I thought I lost my crab. But then the crab showed up TWICE the size it was before. Keep an eye out for your crab and let us know.
10g Nano restarting my addiction all over again!
29g planned for this summer....