New owner with stray crab

[Toad]

So I unexpectedly have a crab. My brother found a large hermit crab eating cat food out of a dish he had outside for a stray cat he feeds on his patio. He lives in the middle of a North Eastern US state, so it's definitely not wild. He couldn’t give it the right setup with his situation right now, so I am taking care of it. It is temporarily in a ten gallon with about 8 inches of sand and coconut mix, a heater, hydrometer, salt and fresh water dishes, a shell and food. I will be setting up a 30g tall (24"l x 24'h x 12"d) with spray foam, cork bark, climbing stuff and 2 deeper water dishes, as well as more sand mix and more shells, although it's hard to get ones big enough around here.

I would like to get him a buddy since they're social, but he's a big crab and I don't know if it would be better to keep him alone since the tank isn't 55g like the size chart said. I also don't know what kind he is. I've thought about trying to get a larger tank, but I live in a small apartment with 2 dogs and a 20g fish tank on the 3rd floor, so it would be hard for us to pull off right now. My brother may be taking him back next year, and if so he can give him a bigger set up. I'd include images but I'm on mobile and not sure how to do that on here.

Thanks

[curlysister]

What used to be thought of as 'social' behaviour is now known to be resource sharing - ie where there are more resources there will be more crabs. So one crab will be just fine alone. If you add another crab into a tank that is too small, you run the risk of aggression or accidental injuries.

[crabocado]

Cool! What a fantasy come true, to have a hermit crab just kind of show up your cat's outdoor food dish. If only the rest of life could be so serendipitous. I hope the little guy didn't suffer too much, considering it's a cool time of year.

[Toad]

OK good to hear, then I will keep him by himself until he has more room. And yeah, it was super odd and we have no idea what led to him roaming around, but he seems to be doing OK so far.

[wodesorel]

Unfortunately its not a crazy rare occurrence to just find wandering hermit crabs in places they have no business being. Kids loose track while playing, or parents dump them outside when they get tired of taking care of them. I'm in Ohio and adopted a crab that a family found out by their garage in October several years ago. This crab is so lucky he found you and your brother!!