How do I know if they are molting? need new shells

[Kelly4779]

Hi, we purchased some 3 hermit crabs and a terrarium from someone approximately a month ago. When we got them, the temperature and humidity were really low, we have been working on that, and finally have both good. Humidity around 85% and Temperature above 80 degrees.
We are currently working on changing the fresh and salt water dishes into deeper pools.
We were planning our next upgrade to be to change the substrate (currently moss and dark sand) to sand/cocofibre mix, and to make the substrate deeper.
When we got the hermit crabs, they did not have any extra shells, we put a few shells in, but they don't seem interested in them.
We were planning on measuring the current shells when we changed the substrate so that we could purchase some new shells in the correct size.
We haven't seen one of the crabs (a young PP) in about 3 days, and rarely see the other two (both older PP). How do we know if they are molting? There have been a lot of changes in the last few weeks, so now sure if they are just hiding, or if they might be molting, or upset with us. We don't want to change the substrate if they are molting.
I know we need some new shells, but how do I know what size to get them if they don't come up often.
any suggestions?

[Hermiesguardian]

Hi, we purchased some 3 hermit crabs and a terrarium from someone approximately a month ago. When we got them, the temperature and humidity were really low, we have been working on that, and finally have both good. Humidity around 85% and Temperature above 80 degrees.
We are currently working on changing the fresh and salt water dishes into deeper pools.
We were planning our next upgrade to be to change the substrate (currently moss and dark sand) to sand/cocofibre mix, and to make the substrate deeper.
When we got the hermit crabs, they did not have any extra shells, we put a few shells in, but they don't seem interested in them.
We were planning on measuring the current shells when we changed the substrate so that we could purchase some new shells in the correct size.
We haven't seen one of the crabs (a young PP) in about 3 days, and rarely see the other two (both older PP). How do we know if they are molting? There have been a lot of changes in the last few weeks, so now sure if they are just hiding, or if they might be molting, or upset with us. We don't want to change the substrate if they are molting.
I know we need some new shells, but how do I know what size to get them if they don't come up often.
any suggestions?

There's a shell guide on here that will at least tell you what type of shell is most preferred. For me, sizing is difficult since I don't handle my crabs. I just kind of eyeball it but I have gotten shells way too big that way. It's possible they are just buried and coming up at night. If you smooth out the substrate you'll see footprints.