HCA: Hermit Crab Association

A few days ago me & my mom recently purchased a hermit crab in the outer banks while we were on vacation. (Back home now!) The hermit crab is going to go to my aunt’s summer school for autistic kids (which I volunteer at) during the “beach” themed week. It came in a extremely small cage, and my mom purchased it from a beach / outer banks beach like shop.
I have tried contacting the shop to ask, however the number is no longer in service (that’s on google maps), and there is no website I can find. The people who work at the shop are also German, which creates a language barrier too. I don’t think the hermit crabs were kept in good conditions either, Bernie (my hermit crab) came in a small plastic cage with wiring (like a travel cage) , a small sponge, a food bowl, a hut (which all had to be bought by my mom) and we have a slightly bigger painted shell.

I’ve researched some, and I am also going to be continuing to take care of the hermit crab, I want Bernie to have a good life. I’ve learned that we need to buy enrichment materials, climbing materials (which, Bernie is doing a lot of!!) , moss (that is non toxic and a safe material, sand, gravel pebbles also seem to be okay? , i also saw that subsate was mentioned, but i’m not sure what it is. I also understand that multiple sponges, shells, and waterbowls are needed (that contain dechlorified watee).

I also already have an aquarium tank at home because of a hamster that we never ended up getting.

I’m a little stuck on what to do, but here are some of my questions :
How can I identify my crab’s species?
Are there any brands that anyone reccomends for me to get?
How can I bond / help support Bernie to feeling safe & comfortable?
What are some brands of dechlorified water? (Bottled water would be the most suitable option due to my situation right now)
Are hermit crabs nocturnal? Bernie seems to be having some activity during the afternoon as well, though I think this could also be because of stress…
How can I identify if the aquarium tank I purchased a few years ago is the right gallon size?

thank you so much to anyone who replies

Welcome to crabbing!
What size is the tank you have?
Substrate refers to what is in the tank for the crabs to dig down into. It can be all play sand, all coco fiber, or a mix of the two. Play sand is cheap, sold in 50lb bags at hardware stores. Many of us mix some coco fiber in with the play sand. It should be moistened to sand castle consistency, and should be at least 2-3 times as deep as your largest crab.
You will need a hygrometer/ thermometer, and you tank should be around 80F and 80% humidity. Crabs have modified gills and need high humidity to breathe. If your tank doesn't have a lid, you will need to get something to cover like plexi glass or glass, or you can cover it with plastic wrap to hold in heat and humidity.
Depending on the temperature of your house, you will probably need a heat mat - they are called 'under tank heaters' but go on the back of the tank, not under the tank.
You should use tap water treated with a dechlorinator (SeaChem Prime is a commonly used brand) for the fresh water. Then add a marine salt (Instant Ocean is a commonly used brand) to make the salt water). No sponges needed, but be sure there is a way for your crabs to crawl out of the pools if they are deep.
We don't really recommend handling your crabs until they have molted at least once with you.
If you haven't already looked at the care sheets, start with the 'basics' one, and go from there. It has a photo of a basic ten gallon tank that contains everything you need.

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