HCA: Hermit Crab Association

I had one go back down for a molt about a month or so after she came up from one. She was an adoptee and the tank that her previous owner had her in only had about a half inch of sand in it. I just figured she needed to get in an extra molt quickly!

However, they might also be buried because they're cold or something.

It depends on the crab and depends on the size. Smaller crabs will molt more often, larger less frequently. They can also do more frequent molts if they have a problem that occurred since their molt - fight and injury to a leg for example - or if they weren't able to fully fix a problem prior to the last molt. If you want to know what is normal for your crabs you can keep a journal of the date the dig down, the date the come up, the length of the molt, and the day between molts. I keep this information in a spreadsheet, but have to admit that I have not been good at keeping it up to date lately.

I had a large once go back under in 10 days. :roll: I've found that teenies go once a month, the smaller ones about 6-8 weeks, mediums two to three months, larges three to five months, extra-larges five to nine months, and then my jumbos go every 12 months nearly to the day!

The temp down to 75 at night should be ok, especially short term, but if it is that low you should try to get it up close to 80 during the day. Placing a lamp near the tank, with the shade off, during the day can help. I've done that in the past as a temporary solution. If you have a pole light around that you can point one of the lights directly at the tank (keep it about 6" away or so) that works well.

Think it depends a lot on the crab. I have teeny/small that has molted twice in 6 months, and is still the same size. I have another who started off small/ Med and is now on his 4th molt in 6 months and is trying to push the large barrier.

My 2 PPs were smallish when I got them, and they were both molting every 1-2 weeks for a few months. I've been blessed with fast molters. They got big in a hurry. Now they've kind of chilled out and only go down about once every 1-2 months. I've had them maybe 7 months or so and we have upgraded shell sizes 4 times on both. They always seem to have synchronized molting.