These are not real shells in use for live hermit crabs. This picture has been around for some time. There is occasionally talk of offering some form of synthetic shell to replace the shells being lost due to collection by humans. Here is another attempt:
This is being done. I just got a hermit crab in a glass shell a few days ago. He seemed highly stressed and didn’t make it. 🙁 I don’t think it was a good form of protection because it was so clear, and it also held a lot of unwanted substrate and dirt. Stick with natural shells.
So my Petco had empty glass shells in the tank this weekend. I was shocked. I asked one of the employees if the shells came empty or with crabs in them. Her response: “There were crabs in them but they immediately switched out of them. They seem to hate them.”
Not surprised… the shells are VERY thick so they would not be an ideal choice. I may buy one of them just to have it though.