HCA: Hermit Crab Association

Hi,
My son got 3 hermitt crabs, we have them in a 20 gallon tank, heat between 75-80, humidity has been a struggle. We've had them for almost two months now and they seem to be doing great, the eat, drink, play, and get along. All of the sudden one keeps going under a log we can see him under there, he's alive but haven't seen him come out in over a week. We also have one that appears to have gone under the substrate. There is some lose substrate in one section. I don't know how to tell where she has tunneled to or if she is just underneath for a moult in that spot. Can anyone help us out on what to look for?

When hermit crabs tunnel, it can be for several reasons:

• they are digging for fun

• they are digging to destress from poor conditions before we had them

• they are digging to molt

• they are digging to hide because they don't like the hiding places we have provided

Unfortunately, it is impossible to know which of the above is the cause. It is never advisable to attempt to dig them up unless there is an emergency, because if they are molting under there, disturbing them would cause significant harm.

They will backfill their tunnels, so the opening they went down in won't be the same one they'll come up in. They can dig another hole.

Does that help?

Is there a way to see where their tunnel is. There are no holes, just substrate that was torn up. We have not touched anything but we have to make some changes to the substrate as we learned we did the wrong parts sand and eco-earth. Also their water baths have sank and need to be cleaned but I'm afraid of collapsing tunnels.

There is no magic mix of substrate! You can use all playsand, all cocofiber, or any kind of mix of the two. So long as it's moist enough that it holds its shape when squeezed without dripping, it's perfect for hermits.

There is no way to check for tunnels. If they're molting they won't actually have any tunnels down there, it'll be one little tiny cave where they've chosen to molt, just large enough to fit inside. You may get lucky and be able to see where they are from the bottom, but they don't always make it to the glass and even a 1/4 of substrate will block them from view

They do unfortunately like to molt underneath objects, so they could be under the water bowls. If you do it carefully, you should be able to gently remove the bowls and then decide whether to keep using them, or put them back overtop any molters and have an alternate source for water until the crab(s) come back up.