HCA: Hermit Crab Association

Hi, I’ve had two hermit crabs for 7 months, Patty and Eugene. A few weeks ago Patty went underground and didn’t surface for a long time. I assumed she was molting, and I knew where she was in the tank. Yesterday I realised that both the shells I recognised the crabs by were empty, so I figured they must have both changed shell on the same night.

I wanted to see what they looked like. I know I’m not supposed to dig around, but one of them was on the surface, and I wanted to know what the other one looked like. A half an hour later and I’m here, the tank empty, and I haven’t found anything other than disembodied crab claws.
I knew I should have gotten an isolation tank, but my family claimed I didn’t need it. Now I’m dreading the thought that Eugene has killed Patty in her molt.

Part of me knows it’s true but I could use more experienced crab owners to help me understand. I thought I was doing everything right, but now my crab has eaten the other and I just don’t know what to do! Am I supposed to get more crabs so Eugene isn’t lonely? I’m just struggling to process it all...

Was there meat inside the claws? If they were empty they may have just been molting residue.


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What type and how deep is your substrate? How big is your tank?

If you fill in the Emergency Template, we might be able to help with what went wrong:

http://www.hermitcrabassociation.com/ph ... 27&t=46102

JoeHermits wrote:Was there meat inside the claws? If they were empty they may have just been molting residue.


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It was really hard to tell. It sort of disintegrated when I touched it, but it was also clogged with sand. Nothing smelt in the tank before, so I though that she was alright. But I’ve searched the entire tank and only Eugene is in there.

Your crab most likely didn't survive the molting process, which is, unfortunately, common for many crabs. Due to the conditions they are shipped and held in, they can sustain injuries or have illnesses that we can't see.

It's not necessary to isolate crabs for molting, provided they have deep enough substrate and plenty of room.

If you found a few bits of exoskeleton, within or next to the shell, then it's more likely the crab died while soft and the body decomposed.



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soilentgringa wrote:Your crab most likely didn't survive the molting process, which is, unfortunately, common for many crabs. Due to the conditions they are shipped and held in, they can sustain injuries or have illnesses that we can't see.

It's not necessary to isolate crabs for molting, provided they have deep enough substrate and plenty of room.

If you found a few bits of exoskeleton, within or next to the shell, then it's more likely the crab died while soft and the body decomposed.



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I couldn’t smell anything in the tank, so I just assumed she was alright. Does that mean Eugene didn’t eat her? And what should I do next time so the next crab does survive the molting process?

curlysister wrote:What type and how deep is your substrate? How big is your tank?

If you fill in the Emergency Template, we might be able to help with what went wrong:

http://www.hermitcrabassociation.com/ph ... 27&t=46102

1. What kind of substrate is used in your tank and how deep is it?
-3 inches of sand on one side and eco earth on the other side. Patty was in the eco earth when I last saw her.

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?
-Yes, but they aren’t digital ones. It usually sits in the “optimal” range of the gauge.

3. Is a heat source used in the tank? If so, what?
-I use a heat pad on the left side of the tank. I also used to use a dull heat lamp in winter.

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)?
-Yes, I have fresh and salt water dishes. I use the Zoomed mixtures that came with my tank and follow the instructions on the bottles.

5. What kinds of food do you feed and how often is it replaced?
I do have a few different commercial brands of food, but I try to put in different things like almonds, cos lettuce, broccoli, carrot, and occasionally ham.

6. How long have you had the crab and what species is it, if known?
-I’ve had them for 7 months. I’m unsure of their species sorry.

7. Has your crab molted, and how long ago did it happen?
-I thought that Patty had begun molting as she disappeared about 4-5 weeks ago, and there hasn’t been any fishy smell to indicate that she died. Now she’s gone entirely.

8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
-I have the Zoomed out, which I believe is a 10 gallon glass tank with a screen lid. I use a damp cloth over half of the lid to keep the humidity in.

9. How many crabs are in the tank and about how large are they?
-Two crabs, Patty and Eugene.

10. How many extra shells are usually kept in the tank, if any?
-8 to 10 spare shells

11. Have there been any fumes or chemicals near the crabitat recently?
-No

12. How often do you clean the tank and how?
-It was last cleaned 3 months ago

13. Are sponges used in the water dish? If so, how are they cleaned?
-Yes, there is one in the salt dish and another in the fresh dish. To clean it I squeeze out the water and leave it to dry in the sun. This may be the wrong way of doing it, sorry.

14. Has anything new been added to your crabitat recently?
-I put in fake plants from Petbarn about a week ago, so they had more places to hide.

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.)?
-Nothing else really

16. Please describe the emergency situation in detail.
-I’m pretty certain that Eugene has eaten Patty, as I can’t find her anywhere in the tank. I could only find disembodied crab claws while searching, and nothing smelt in the tank so I didn’t think she had died during her molt. I’m unsure what to do now. I can’t leave him by himself in the tank, but is it wise to introduce new crabs? Will he attack or will they attack him? Thank you for helping!

It's more likely that conditions contributed to the death than the other crab eating it.

Unfortunately there is a huge amount of misinformation about how to care for hermit crabs and they really do require some specific conditions to thrive.

Heat and humidity should be above 75% and 75°F. 80/80 is a good level, with more activity observed in mid 80's.

Commercial pellet foods usually contain ingredients that are toxic to the crabs so we don't recommend them.

They need an ocean salt substitute for water such as Instant Ocean, which is a salt crystal powder mix that is mixed with dechlorinated water. They also need a dechlorinated fresh water dish as well. The Zoomed dechlorinator works but is really not cost effective and does not provide adequate minerals or salt solution for them.

Substrate should be 3X deeper than your largest crab, ideally a mixture of playsand and eco earth, mixed with dechlorinated water to a consistency that you can make sandcastles with. Not too moist but will hold shape when molded.

They make caves underground to molt in so having adequate substrate is essential to a successful molt.

Dried insects like crickets and grasshoppers, mealworms, river shrimp, krill, dried or fresh bits of fish or proteins, leaf litter, veggies, fruit, eggshell, bee pollen, raw unpasteurized honey, and other foods off of the "Safe List" make up a healthy diet for land hermits.

The basic essentials they need for survival are substrate, heat/humidity, waters, and food.

They love to climb and need plenty of hiding spaces.

If your crabs are very small then 2 could live in a 10 gallon until they outgrow it.

Petco often has dollar per gallon sales or you could check Craigslist or OfferUp. A 29 is a good size to start or alternatively you can get a large clear tote at Walmart or Target.

Other members will also chime in but I suggest an Acurite digital guage. They are fairly cheap and last for a long time. They will give you a more accurate reading for heat and humidity because the little analogue ones are notorious for being wrong.

I have to sign off for now but I highly suggest reading the care guides and making some upgrades before adding another crab.

Don't feel too bad about this; even experienced crabbers have losses. Some seem to be more delicate than others in captivity and they really just werent meant to be pets. They are collected in the wild and shipped around the world and held in awful conditions and then pet shops don't offer good care advice.




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The only thing I would add to what soilentgringa said is that substrate needs to be a minimum of 6" or 3x the height of your biggest crab. Whichever is deeper wins.

You can seal the lid by taping saran wrap to the entire lid. They will get air exchange when you feed them. This will keep in the humidity.
And the Accurite thermometer/hygrometer is the way to go. The "dial" guages are highly inaccurite. Sponges are an old practice and they hold bacteria. The pools need to be deep enough for the crabs to fully submerge with a safe way to get in and out. If you add another crab just dip him in the freshwater (dechlorinated) pool so he doesn't smell like a stranger.

Thank you so much for all the advice! Im planning to upgrade the tank before adopting anymore crabs. Will fish aquariums work for hermit crabs? I’ll definitely put more substrate in my next tank as well, but should I remove the sponges from the water dishes then? I don’t want them to make my crabs sick.

KraaiTheWolf wrote:Thank you so much for all the advice! Im planning to upgrade the tank before adopting anymore crabs. Will fish aquariums work for hermit crabs? I’ll definitely put more substrate in my next tank as well, but should I remove the sponges from the water dishes then? I don’t want them to make my crabs sick.

Fish tanks are fine. Yes, remove the sponges. They don't need them to drink.

Hi just a quick update: I’ve upgraded to a 65L tank and now have 6 inches of playsand and coconut husk for substrate, and I’ve also added a climbing rope, fake stump, two climbing logs and varies plastic plants. I’ve removed the sponges and thankfully the lid helps keep a lot of the humidity in, though I’m still waiting for my Acurite thermometer to arrive. Also I’ve ordered Seachem Prime and Instant Ocean so I don’t have to use the Zoomed brand anymore.

I just have two last questions, first being what method do you use to make small quantities of dechlorinated water with the Prime? The instructions on the back say 5ml makes 200L, so each ml can make about 40L. How do you guys make smaller quantities than that?

And secondly I introduced Eugene to the new tank yesterday and he seemed very pleased. He was exploring it all of yesterday and climbing which was lovely to see. I’m wanting to introduce new crabs to the tank, but I just need some advice on how to do so. I was wanting to adopt two more but I was worried they might all fight one another, as I’ve heard it can get violent when they first meet. Should I put the two new crabs in a seperate tank temporarily, and then introduce them to Eugene separately or together?

Thanks for all your help!

KraaiTheWolf wrote:Hi just a quick update: I’ve upgraded to a 65L tank and now have 6 inches of playsand and coconut husk for substrate, and I’ve also added a climbing rope, fake stump, two climbing logs and varies plastic plants. I’ve removed the sponges and thankfully the lid helps keep a lot of the humidity in, though I’m still waiting for my Acurite thermometer to arrive. Also I’ve ordered Seachem Prime and Instant Ocean so I don’t have to use the Zoomed brand anymore.

I just have two last questions, first being what method do you use to make small quantities of dechlorinated water with the Prime? The instructions on the back say 5ml makes 200L, so each ml can make about 40L. How do you guys make smaller quantities than that?

And secondly I introduced Eugene to the new tank yesterday and he seemed very pleased. He was exploring it all of yesterday and climbing which was lovely to see. I’m wanting to introduce new crabs to the tank, but I just need some advice on how to do so. I was wanting to adopt two more but I was worried they might all fight one another, as I’ve heard it can get violent when they first meet. Should I put the two new crabs in a seperate tank temporarily, and then introduce them to Eugene separately or together?

Thanks for all your help!

Glad things are going well. I use a gallon jug, like a water jug, and just drop in one drop of prime into the water. That way I have water that will last awhile. Same for the salt water. But what I found out the hard way is to add the salt first into an empty gallon jug, then fill it with water, then add the drop of prime.
As for introducing new crabs, give them a quick dip in the freshwater pool to wash off "stranger" smell. Then put them in the tank. That's it. They'll probably all have antenna fights to establish dominance.

The one thing I want to add, I may have missed someone else mentioning it though. Your substrate needs to mixed with dechlorinated fresh, or salt water to s sand castle consistently. THIS IS VERY IMPORTANT. If the substrate is too dry the crabs will not be able to dig tunnels and molt properly.

I believe we lost one of our crabs several months ago to a similar incident as you. We later we found out that our humidity gauge was not working properly and it was too dry in the tank. I think after he shed his exoskeleton and was still soft the dry sand dried him out before his new exo hardened.

Hermiesguardian wrote:

KraaiTheWolf wrote:Hi just a quick update: I’ve upgraded to a 65L tank and now have 6 inches of playsand and coconut husk for substrate, and I’ve also added a climbing rope, fake stump, two climbing logs and varies plastic plants. I’ve removed the sponges and thankfully the lid helps keep a lot of the humidity in, though I’m still waiting for my Acurite thermometer to arrive. Also I’ve ordered Seachem Prime and Instant Ocean so I don’t have to use the Zoomed brand anymore.

I just have two last questions, first being what method do you use to make small quantities of dechlorinated water with the Prime? The instructions on the back say 5ml makes 200L, so each ml can make about 40L. How do you guys make smaller quantities than that?

And secondly I introduced Eugene to the new tank yesterday and he seemed very pleased. He was exploring it all of yesterday and climbing which was lovely to see. I’m wanting to introduce new crabs to the tank, but I just need some advice on how to do so. I was wanting to adopt two more but I was worried they might all fight one another, as I’ve heard it can get violent when they first meet. Should I put the two new crabs in a seperate tank temporarily, and then introduce them to Eugene separately or together?

Thanks for all your help!

Glad things are going well. I use a gallon jug, like a water jug, and just drop in one drop of prime into the water. That way I have water that will last awhile. Same for the salt water. But what I found out the hard way is to add the salt first into an empty gallon jug, then fill it with water, then add the drop of prime.
As for introducing new crabs, give them a quick dip in the freshwater pool to wash off "stranger" smell. Then put them in the tank. That's it. They'll probably all have antenna fights to establish dominance.

Thank you for the advice! I introduced my two new crabs, Larry and Sandy a few days ago, and they have all been getting along quite well! Thank you for the tip about the Instant Ocean too! I’ll keep that in mind when I make the next lot.