HCA: Hermit Crab Association

I recently got a new hermit crab. This hermit crab who’s name is Bella, is worrying me a lot because she digs a hole for herself and buries herself for a very long time and then resurfaces for a day or two. This has been happening for a while now and I’m getting very worried, as she might die soon. Please help.

How are your tank conditions now?
Do you have a thermometer and hygrometer - what are the readings?
What size is your tank?
What do you have for substrate and how deep is it?

I have a ten gallon tank, a hygrometer and thermometer, and I use coco fiber and some sand as substrate but I am planning to change it to 5 parts sand.

My substrate is about 1 inch deep but I do plan on adding more once she comes up again.
Edit: My thermometer is at 64 Fahrenheit and my hygrometer is at 72 humidity.

Your heat and humidity are both too low for crabs to survive for very long.
Do you have a lid on your tank? If not, you can cover it with plastic wrap to help keep the humidity in.
Are you using a heat mat on the back of your tank? If not, you need to get one. If so, some types can be insulated over top - otherwise you can insulate around it and on the sides. You can also add a folded up blanket on the lid.
You don't need to have a specific ratio of sand to coco fiber - you can use all one or all the other, or a mix in any ratio. You can also add sub while a crab is underground, just don't drop it in from any height, or pack it down.

Thank you! I will be getting a heat mag for them soon! I currently have foil taped to the top of their tank.

Thank you! I will be getting a heat mat for them soon! I currently have foil taped to the top of their tank.