HCA: Hermit Crab Association

So I'm crab sitting for my girlfriend while she's away.

The tank is at my house and her crab began to burrow Sunday night. It's still under with no signs that it surfaced during the nights.

Is it safe to transport the tank back to GF's house when she's back from vacation, or does it need to stick around here until little Jade surfaces?

How big is the tank? It may not be wise to move if it's not an emergency situation because moving the tank can shift the substrate and bring it down on them. If there is no problem with keeping the tank til Jade comes back up I'd recommend that. If it's an absolute need to move it, then you have to be extremely careful or even consider digging Jade up so the substrate doesn't collapse on them. If you end up keeping Jade keep in mind they could be down for weeks/months before resurfacing.

Yes, I agree. Move the tank when all crabbies are up! Better safe than sorry!

A week after GF is back, I go on my week-long family vacation.

If she's down and presumably molting do I just leave her plenty of water and dry food for that week?

Also: Tank is 5 gallon and has a solo crab.

She may not even be up to eat or drink while you're away. But you can toss some food in to be safe (nothing that rots quickly) and top the water off, she should be fine for a week. You may find nothing is even touched.

I would recommend a larger tank and a friend down the line, but that's up to your gf.

I've also been having humidity trouble, and I'm trying the saran wrap method.
Is that safe to leave on for a week? I feel like people who use that are opening up the lid at least once a day for food and water so air also gets in.

Maybe leave it with a couple small holes, but it should be fine.

GF is insisting on taking Jade home when she gets back despite the danger. Of all two options, is carefully digging her out safer than trying to not collapse her tunnel?

How deep is the sub and what kind of sub is it? I wouldn't really dig her up, if it's a 5g it doesn't sound like it's going to be that deep. So not much might shift.

About 5 inches and it's pretty much all EE.