HCA: Hermit Crab Association

Has anyone ever experienced their hermit crab emitting a strange smell? Almost like a very strong musty deceased crab smell. The crab is very much alive. I moved him to a new ISO tank, disposed of the substrate he was in, and the problem was gone. Around 24hrs later the smell is back in the new ISO tank coming from the moss pit. Sure enough, the same crab is in there. Does anyone have any idea what could be going on?


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My P.P has a natural musk and I assume all hermit crabs do, but if it’s more of a fishy smell then I’m not sure.

Are the water pools that you provide him/her with deep enough for him/her to fully submerge in and safely get out of?

Hermit crabs keep water in their shells. It could be the water in his shell that smells so bad. If his water is dirty, perhaps that is what stinks.

SantiClout wrote:My P.P has a natural musk and I assume all hermit crabs do, but if it’s more of a fishy smell then I’m not sure.

My husband describes it as more musky/moldy smelling. Is that what your crabs is like?


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GotButterflies wrote:Are the water pools that you provide him/her with deep enough for him/her to fully submerge in and safely get out of?

Hermit crabs keep water in their shells. It could be the water in his shell that smells so bad. If his water is dirty, perhaps that is what stinks.

Yes, he does. That could be it, but here is what has me stumped...When I took him out of the original ISO tank I did sniff him and he had no smell at all. It was coming from the substrate surrounding him. In the new ISO tank, right when the smell reappeared, I sniffed him again and it was definitely coming from him. I’ve heard some crabs will emit a hormone that causes a smell when they are trying to fend off predators. Could this be the case?

A little bit of a back story, this crab has been strange from the beginning. He’s the only crab I’ve ever had that will only wear murex shells. He was in a very oddly modified murex shell when I got him. I purchased him at PetSmart when I was there buying supplies for my new Crabitat build. I saw one tiny PP and two Jumbo PP’s in horrible conditions. No water or food, gravel substrate, etc. I do not like to support pet stores but I felt so bad for these guys and had to get them out. The one that has the strange smell is the tiny one. His big pincher is a beautiful red color, so he appears to be getting the nutrients he needs and is healthy. I’ve never seen his entire body. He will not come out when people are around at all. If I didn’t know better I would think he was just a phantom shell!

I just can’t figure out this smell issue and don’t want to add him to my main Crabitat until I can safely rule out possible disease. I purchased him on June 4th. So going on almost 2 months now. Posting a picture of the shell he came in. Maybe we can rule out shell rot at least?


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Interesting. That shell is funny! It looks like a tunnel! I think a person did that!

You would see shell rot, and I don't think that shell rot has a smell to it. You are wise to keep him separate until you know for sure. You could always do medicinal baths on him/her and treat him/her for it. It wouldn't hurt the crab.

It could also have a weird growth that you just aren't able to see. We had a member on here about 4-5 years ago that purchased a strawberry that had a tumor/growth near it's abdomen. She saw it when it was doing a shell change. It ended up passing away.