HCA: Hermit Crab Association

Thank you for your help! My mom found a tank which is a 40 gallon so once I get sand I'm going to put them in there. Also when they are done from molting

Update: I set up the backup tank and as soon as the other crab comes up I'll put him in there

So my stupid self brought another hermit crab who's medium sized when I have two largish ones in a 20 gallon. I have a 10 gallon but it isn't set up yet. What should I do because I can't afford a new tank yet till probably a month or so. I feel so bad and I'm scared one of them is gonna die especial...