HCA: Hermit Crab Association

Since you've come to the emergency forum, we know you want a fast answer to your question. In order for us to figure out the problem as quickly as possible, we ask that you answer the following questions as best you can. Some of them may seem odd, but they're all designed to give us the information we need to give you a good solution for your problem. The things in the [ brackets ] are there to make this post easier to read once submitted. Thanks!


1. What kind of substrate is used in your tank and how deep is it?
I have 3 PP’s in 6-7 in of 5 parts play sand to 1 part eco earth.

2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read?


3. Is a heat source used in the tank? If so, what?
They have a heat mat on the back side of the tank.

4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)?
And both fresh and saltwater pools available made with instant ocean and seachem prime are available to them.

5. What kinds of food do you feed and how often is it replaced?
They also get a large variety of different proteins, fruit, veggies, carotenoids, green sand, worm casings, etc

6. How long have you had the crab and what species is it, if known?
Of the 2 crabs in question we’ve had one for 8 months and the other for about 4 months.

7. Has your crab molted, and how long ago did it happen?

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
They are currently in a glass tank with a glass lid.

9. How many crabs are in the tank and about how large are they?
There are 3 crabs in the tank but the 2 in question are about the size of a half dollar or slightly smaller.

10. How many extra shells are usually kept in the tank, if any?
6 or more larger shells per crab are available to them to change into.

11. Have there been any fumes or chemicals near the crabitat recently?
There have been no fumes or chemicals near them.

12. How often do you clean the tank and how?
I clean the food and water daily or every other day, by taking it out and changing it before they have a chance to bury any or for it to get moldy.

13. Are sponges used in the water dish? If so, how are they cleaned?
They don’t have any sponges, just ways for them to get in and out of the water pools

14. Has anything new been added to your crabitat recently?
And nothing new has been added recently.

15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)?


16. Please describe the emergency situation in detail.

So yesterday 5/7/22 at 5:30 am as I was coming out to change my crabs food and water I noticed my largest crab the one we’ve had for 4 months who has been molting for about 4 weeks coming out of his molting hole/tunnel (we’re in the process of changing to a bigger tank and making this one the iso tank so this is why the other crab was in the same tank) I thought that was a short time for a crab his size to finish molting so I looked closer and noticed it was not my molter but my slightly smaller crab who I’ve had for 8 months coming out with the bigger crab (my molters) shell on. Inside the hole was my totally limp molter (who I believed to be dead) and the slightly smaller crabs empty shell and what I believe to be most if not all of the molters exoskeleton. My slightly smaller crab who had more than enough larger shells to choose from and more than enough protein to eat had dug my molter up and took his shell. I panicked as I’ve only owned them for 8 months and had heard of this happening but didn’t know exactly what to do. Apparently I must’ve caught the shell thief right after or during, as he was trying to get back in the hole, to I assume eat the molter or his exoskeleton. As I said I panicked and I thought the molter was dead, I gently scooped under the sand to remove him with a spoon and put him in a tiny tank just big enough for some substrate, his body, a shell and his exoskeleton as I didn’t smell a death smell but had to get him away from the other crab that dug him up and collapsed his tunnel/hole. While doing this the shell thief decided he didn’t like that shell I guess and switched to another that was available, I then put the molters original shell back in with him when I saw him move slightly realizing he’s alive! I don’t know what exactly happened and I thought the molter had lost a leg and big claw during the attack as I couldn’t see them on him, but today I found him standing and it looks as if he didn’t lose any limbs after all!! As I said he is now isolated in the main tank with his exoskeleton which I crushed up for him thinking he had lost his large claw (he didn’t), and his original shell. When I first found him in the hole yesterday his entire body was whiteish/pale pink and very very soft looking, today his legs and claws have regained some color and looks like they have slightly hardened but are still pretty soft. The problem is idk if he was pulled out of his shell during the attack or if he had yet to get back into it yet during the molt when he was attacked, but he is still not back into his shell, he looks very weak but definitely more lively than when I found him as he’s actually standing and has a leg holding onto his shell now but is still not really moving. How long can he be out of his shell? Should he be able to get back in on his own? Should I keep him in the dark 24/7 like if he was still molting. I really want to help him and for him to survive and I’m not sure what to do. Also why my other crab dug him up? He had more than enough shells and protein as I had recently increased protein due to him being a pretty aggressive crab in general, which seemed to help as he hadn’t been that way in about 2 months until now.

1. What kind of substrate is used in your tank and how deep is it?
I have 3 PP’s in 6-7 in of 5 parts play sand to 1 part eco earth.

2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read?
Curly - What are your temp and humidity readings?

3. Is a heat source used in the tank? If so, what?
They have a heat mat on the back side of the tank.

4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)?
And both fresh and saltwater pools available made with instant ocean and seachem prime are available to them.

5. What kinds of food do you feed and how often is it replaced?
They also get a large variety of different proteins, fruit, veggies, carotenoids, green sand, worm casings, etc
Curly - Crab also need a source of calcium daily.

6. How long have you had the crab and what species is it, if known?
Of the 2 crabs in question we’ve had one for 8 months and the other for about 4 months.

7. Has your crab molted, and how long ago did it happen?

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
They are currently in a glass tank with a glass lid.
Curly - What size is your tank?

9. How many crabs are in the tank and about how large are they?
There are 3 crabs in the tank but the 2 in question are about the size of a half dollar or slightly smaller.

10. How many extra shells are usually kept in the tank, if any?
6 or more larger shells per crab are available to them to change into.
Curly - HCA recommends 3 to 5 extra shells per crab, so for three crabs from 9 to 15 shells. Be sure to look at the 'shells' care sheet for the preferred type of shells for the type of crabs you have.

11. Have there been any fumes or chemicals near the crabitat recently?
There have been no fumes or chemicals near them.

12. How often do you clean the tank and how?
I clean the food and water daily or every other day, by taking it out and changing it before they have a chance to bury any or for it to get moldy.

13. Are sponges used in the water dish? If so, how are they cleaned?
They don’t have any sponges, just ways for them to get in and out of the water pools

14. Has anything new been added to your crabitat recently?
And nothing new has been added recently.

15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)?


16. Please describe the emergency situation in detail.

So yesterday 5/7/22 at 5:30 am as I was coming out to change my crabs food and water I noticed my largest crab the one we’ve had for 4 months who has been molting for about 4 weeks coming out of his molting hole/tunnel (we’re in the process of changing to a bigger tank and making this one the iso tank so this is why the other crab was in the same tank) I thought that was a short time for a crab his size to finish molting so I looked closer and noticed it was not my molter but my slightly smaller crab who I’ve had for 8 months coming out with the bigger crab (my molters) shell on. Inside the hole was my totally limp molter (who I believed to be dead) and the slightly smaller crabs empty shell and what I believe to be most if not all of the molters exoskeleton. My slightly smaller crab who had more than enough larger shells to choose from and more than enough protein to eat had dug my molter up and took his shell. I panicked as I’ve only owned them for 8 months and had heard of this happening but didn’t know exactly what to do. Apparently I must’ve caught the shell thief right after or during, as he was trying to get back in the hole, to I assume eat the molter or his exoskeleton. As I said I panicked and I thought the molter was dead, I gently scooped under the sand to remove him with a spoon and put him in a tiny tank just big enough for some substrate, his body, a shell and his exoskeleton as I didn’t smell a death smell but had to get him away from the other crab that dug him up and collapsed his tunnel/hole. While doing this the shell thief decided he didn’t like that shell I guess and switched to another that was available, I then put the molters original shell back in with him when I saw him move slightly realizing he’s alive! I don’t know what exactly happened and I thought the molter had lost a leg and big claw during the attack as I couldn’t see them on him, but today I found him standing and it looks as if he didn’t lose any limbs after all!! As I said he is now isolated in the main tank with his exoskeleton which I crushed up for him thinking he had lost his large claw (he didn’t), and his original shell. When I first found him in the hole yesterday his entire body was whiteish/pale pink and very very soft looking, today his legs and claws have regained some color and looks like they have slightly hardened but are still pretty soft. The problem is idk if he was pulled out of his shell during the attack or if he had yet to get back into it yet during the molt when he was attacked, but he is still not back into his shell, he looks very weak but definitely more lively than when I found him as he’s actually standing and has a leg holding onto his shell now but is still not really moving. How long can he be out of his shell? Should he be able to get back in on his own? Should I keep him in the dark 24/7 like if he was still molting. I really want to help him and for him to survive and I’m not sure what to do. Also why my other crab dug him up? He had more than enough shells and protein as I had recently increased protein due to him being a pretty aggressive crab in general, which seemed to help as he hadn’t been that way in about 2 months until now.
Curly - Crabs do not leave their shell to molt. A naked crab will die. There is a care sheet that explains what to do for a naked crab, and how to get him to hopefully take a shell on his own.
Depending on the type and size of shells you have, he may have been looking for a new shell. Or he may have come across the molting crab accidentally when digging. If your substrate is not at least two to three times as deep as your largest crab, or you tank is too small, they can either smell the molting crab, or have a higher chance of accidentally digging up a buried crab.

Thanks so much for replying so quickly. I had heard they left their shell to molt but there’s so much wrong info out there it’s hard to know what to believe so thank you for clearing that up for me. So I have a 29 gallon tank (in process of upgrading to a 40) with around 6 3/4 to 7 in of substrate and I forgot to add calcium in my post above, but they definitely get plenty of that as well, they love eggshells and cuttlebone. My largest crab the one who was dug up/attacked uses shells with openings of about 1 1/4 to 1 3/8 in size if that helps determine his size, the substrate is definitely 2-3x his size tho. The readings on my thermometer/hygrometer state that my temp is 77 degrees and humidity 80%. I’m starting to think the other crab that dug him up happened upon him by accident as he’s still digging and looks to be in the beginning stages of molting (eating a ton, a little paler, staying in the pools a ton, digging a lot, etc).I had looked at the care sheet before posting but didn’t know if it applied to crabs in the middle of a molt and I was worried about putting my molter in a dish of water with his shell to coax him back in as as the sheet states, as he was still very limp and lethargic even while standing and extremely soft and pale. So I was nervous he would drown not being able to stand at the time (he was laying on his side) and I had read somewhere not to add any water to a molting crab as their body can’t handle it at that time but wasn’t sure again how true that was but I also knew he would die without his shell. But he’s been nibbling at his exoskeleton all day yesterday and I just woke up and checked and he’s back in his shell! He was flipped on his back tho and didn’t have the strength to get himself up so I gently helped just hold the weight of the shell so he could turn and position himself better the way he wanted to as he was trying but really struggling. He’s still very soft and pale but definitely looks better than the conditions I found him in. Keeping him in isolation until he eats all of his exoskeleton and is back to himself, crossing my fingers that he makes it. I’ll also try out some new shells for my other guy as he seems to still be checking different shells out as well. Any advice you have is greatly appreciated, I’m pretty new to this but see so many ppl doing the wrong things that I’m trying my best to educate myself, no animal should be treated the way some ppl treat these babies.

The care sheet says to put 1/4" of dechlorinated water in the dish.....but it can be less that than, basically just enough to cover the bottom so the crab stays humid and doesn't dry out.
Crabs in the middle of a molt are very vulnerable, so the less handling the better, but that has to be weighed with getting them back into a shell - they will for sure die if out of a shell, and maybe die in one.
As for there being so much info online....when I got my crabs I found HCA, and decided that I would stick to just one source for info, to avoid contradictions. I have now had my two crabs for 11 1/2 years, so I am confident that the advice on this page is solid.

Thanks so much I’m definitely going to stick with HCA. He got back into his shell yesterday with a tiny bit of help and seems to be slightly more active and getting a little harder both last night and tonight. Praying he makes it and just grateful I caught it when I did and not any later as it could’ve been really bad. I have him in iso with just his exoskeleton which he seems to be eating but isn’t finished with it. Should I add any types of his other food or any water for him yet or should I wait until he gets his strength back and hardens up more? I also ordered some more shells in different sizes as the crab that dug him up really seems to want to change shells but doesn’t like any of the 6-7 I have in there for him and I’m thinking that might be part of the issue cuz he was definitely more interested in taking the molters shell than he was in eating him (at least at the time I caught them).