The Crab Street Journal Caresheets

HELP! My Hermit Crab has left its shell! What do I do?

A hermit crabs shell serves two purposes: first protection of the soft abdomen and second it prevents dessication (drying out). A hermit crab that has left the protection and life-sustaining seashell home is telling you it’s in distress.

Coenobita brevimanus shellless

Coenobita brevimanus shellless


  • Physically stressed from poor handling or conditions during capture, transport and/or poor pet store conditions
  • Shell fight-another hermit crab has taken its shell-no suitable shell remains
  • Changing shells and let go of the old one, which was shell-napped by another crab-no suitable shell remains
  • Foreign body/irritant in the shell (sand, pest, fungus NOTE: crabs have been known to hide food in their shell)
  • Temperature is too HIGH
  • Humidity is off
  • Pre-molting, although it rarely happens


Below we expand a bit on these causes.

Physical Stress

Land Hermit Crabs endure a great amount of stress before reaching the pet store. The harvesting and shipping of hermit crabs is a very inhumane process and the crabs suffer because of it. They then arrive in pet stores, who in most cases, don’t know how to properly care for them. They arrived stressed out, dehydrated and hungry. Then you purchase them and take them home. Now severely physically damaged the hermit crab will often leave its shell to die.

Shell Fight

If there is not a variety of appropriate styles and sizes of extra changing shells in the crabitat for the hermit crab to choose from, there may also be shell fights. This is normally dangerous for the hermit crabs within the crabitat due to the fact that hermit crabs would rather let themselves be pulled apart as opposed to giving up their protective home. Many times this leads to a hermit crab being seriously injured or even killed by the aggressive hermit crab in search of a comfortable shell.
There are times too when a hermit crab is shell shopping and may of let go of his original shell to try another on and has his shell taken by another tank mate. This forces the hermit crab to find another shell, if a suitable one isn’t available it is left homeless.

Foreign body

Something may have got into his shell and is irritating his soft abdomen. One can rinse the shell out with dechlorinated water, but many times if something is lodged within the shell this doesn’t help much. Boiling the shell in dechlorinated water and giving it a good shake will many times dislodge anything that may be within it. There maybe pests or a fungus within the shell that is irritating his abdomen and will cause him to leave the shell.

Incorrect environment – too hot, too much or too little humidity

If the hermit crab is too warm, to try to cool off a hermit crab will leave their shells. To prevent over heating it is very important to monitor the substrate temperature as well as the air temperature. The temperature at the warm end of the crabitat should be approximately 80-82F.  At 85F or higher this is nearing too warm for most hermit crabs to be comfortable (some species do enjoy higher temperatures). The temperature at the cool end of the crabitat should be approximately 72-75F. Hermit crabs are ectothermic creatures and must have the variance of temperatures to self regulate.

If the humidity level is too low in the crabitat hermit crabs feel as though they are suffocating. In hopes of relieving the discomfort they are experiencing they leave their shells. If they had been subjected to a too low humidity, too many times it has already caused irreversible gill damage. For a more accurate humidity percentage reading level, the humidity gauge should be located close to substrate in the middle of the tank away from water sources that can affect the gauges reading. The safe range is 70-80% relative humidity. Cheap analog gauges from pet stores are rarely accurate.

Please calibrate your humidity gauge to ensure how accurately it is reading:

A hermit crab will also leave their shell due to a too high of a humidity percentage. A high humidity level makes it difficult for the hermit crab to breath due to the ‘thicknesses’ of the humidity. If subjected to a too high humidity level, this can promote a gill infection that may cause irreversible damage. Maintaining humidity levels of 90% and higher is discouraged.

And even though it is rare, he maybe in premolt or be molting. Pre molt symptoms

How to gently coax a hermit crab back into their shell

Wash your hands.

For a hermit crab who has gone naked to surface molt or come up from molt naked and still soft please jump down to the NOTE section.

Rinse or boil the shell in dechlorinated water and shake it to remove anything that maybe lodged within it. Pour out most of the water from the shell. Place the shell in the bottom of a cup or small bowl depending on the size of the crab. The container should be JUST big enough for the crab and the abandoned shell. Add a small amount of dechlorinated water the bottom of the cup. This will help keep the crab moist and may help the crab re-shell.

Wash your hands.

If the hermit crab is not in mid molt or still soft from molt, gently pick the hermit crab up by lightly holding it just behind the last pair of walking legs. You can also use a large spoon to scoop him up very gently. Carefully examine the abdomen for any signs of irritation being very careful he does not attempt to escape and injure/kill himself. Examine for any molting symptoms as in transparent eyes, lifting of the old exoskeleton, water sac, etc. Lethargy can be a sign of pre-molt or death.

Lower him into the cup next to his shell. Cover the cup with a washcloth to make it dark. Transfer the cup to an isolation unit where the temperature and humidity are within proper ranges OR back into the main tank. Ensure other crabs in the tank are not able to climb into the cup.

Leave the hermit crab in darkness and quiet for a while and it may return to the shell.

After a few hours if the crab still has not re-shell you can attempt to manually place him back in his shell. If the crab is visibly weak it likely will not be able to hold the shell, if this is obvious do not attempt to manually re-shell.

Being very careful and gentle moisten/mist or dip the hermit crabs abdomen with dechlorinated water and try to slide the tip of hermit crabs soft abdomen within his moistened shell making sure it does not scrape or injure the hermit crab. It may be easier to prepare a dish of dechlorinated water, then place both the shell and crab in the water. The buoyancy will make it easier to coax the abdomen into the shell.

If the crab will not or can not hold on to the shell do not continue to force. Try a couple of times and then stop. If the crab is still naked you can move to a slightly larger containment area like a small kritter keeper. Add a few more shells that might fit the naked crab to the kritter keeper. Transfer the naked crab and the original shell to the kritter keeper. Offer some honey, worm castings, scrambled eggs or other favorite food to encourage eating. Place the kritter keeper inside of your isolation tank or in the main tank. It is important the hermit crab remain in the correct heat and humidity.

If the crab still will not take a shell there is little else to do but keep him comfortable and wait. Continue to offer food and water, maintain humidity and heat.

Note: Molting or recently molted crabs should be handled differently. If the crab is still soft or molting, use our 2 liter bottle method (cut off the bottom and place over the crab like a dome) to isolate the crab within the tank. Be aware this does not protect from crabs digging in from below so please keep an eye on the crab. If your other crabs seem overly interested you may need to transfer the crab to a secure container within the crabitat. Use a clean glad ware type bowl with a lid. You can poke holes in the lid. Use a clean spoon or similar scoop to gently scoop up the crab by digging slightly into the substrate below him so that the body is still resting on the substrate and not touching the scoop. Gently place in the bowl along with the most recent shell and one or two other options.  Do not add water to this bowl because of the soft exoskeleton. The crab is going to be exhausted and likely will be unable to take a shell until it has fully hardened and regained energy.  If the shed exo is available be sure to put it in the bowl along with some water and other foods.  Our Hermit Crab Feeding Guide can direct you to the most beneficial foods at this time.

If you need any further help, please read the Emergency Help Article.

Substrates for Hermit Crabs

The commonly used and recommended substrate is 5 parts play sand to 1 part cocofiber. The other sands or stones listed here are safe for using in your crabitat in select areas but not as the primary substrate. Hermit crabs require deep, moist sand to burrow and molt properly.


Beach sand

Beach sand

Collecting sand from the beach is not advised. In most areas it is illegal to take sand from the beach. In many areas of the world the beach sand is heavily contaminated from polluted waters.

Most owners use play sand found at their local hardware store. Please take note of the quality when purchasing play sand. If in doubt ask other hermit crab owners what they use and ask how it works when damp. Some play sands are low-grade sand made from crushed rocks and have impurities since they are used for the building industry. Choose a play sand intended for a children’s sand box; this is good quality sand and has been cleaned and sanitized.

If in doubt as to the quality wash and bake your sand the first time you use it. However, not all impurities can be washed, boiled, or baked out of a substrate. Cleaning and drying sand can be messy. Make sure you cover the drains or use a plug when rinsing. Most rinse their sand and then dry it before returning it to a cleaned crabarium. Another alternative is to take the sand outside and place it in a bucket, use a hose to rinse the sand until the water runs out of the bucket and is clear. To drain the sand, place the sand into a pillow case so that your drains are not blocked up. Poor quality sand may also have metal shavings, test with a magnet. If you find metal shavings in the sand do not use it.

The positives of sand include that it is attractive to look at, especially after some heavy hermit crab traffic, with their little marks in the sand. Hermit crabs love tunneling down in sand but you must be careful that you keep an eye on the level of dampness. If there is standing water or food items in damp sand you may develop mold (mould) or bacteria. This leads to a weakened condition, stress to the hermit crabs and can mean possible death. Many use a kitty litter scoop or sieve to pick through the sand on a regular basis to remove uneaten food or refuse. Another alternative is to add isopods to your tank to keep the substrate clean.

The ideal primary substrate in your tank should be a good quality play sand with some coco fiber mixed in. The coco fiber can help with aeration in the sand as well as add humidity. This is the most common approach but some use straight play sand. Straight cocofiber is NOT recommended as it can causing molting deaths or abnormalities.

These other substrates are safe to use in your tank but should not be your primary substrate as they do not allow for proper burrowing and molt cave building.

River Pebbles

River pebbles

River pebbles

Inexpensive and great remedy for sandy feet by for placing around the water dish. Hermit Crabs often wade through the water dish and then onto sand which then sticks to their wet exoskeleton. Placing river pebbles gives them a ‘drying off’ place and offers more traction. Make sure that the river pebbles that you purchase are NOT coated with resin or paint. DO NOT HEAT/BOIL/BAKE ROCKS. There are many natural river pebbles which are not coated around. One brand to ask for is Ultrastone Natural River pebbles.

Coral Sand and Reef Sand – versatile yet fragile

Coral Sand

Coral sand

Coral sand can be purchased per pound/kilo from your local fish / aquarium store. It can be expensive but it is a wonderful source of calcium for your land hermit crab. It is similar to Aragonite sand. Keep an eye on the coral sand for if it gets too damp it can disintegrate so try to keep it at ‘sandcastle sand’ consistency.

“[Coral sands] are larger grit substrates rich in calcuim and trace minerals, crabs love it. Reef sand & gravel are often very dusty so you have to rinse & dry before use of shake it out well (I used to use a strainer outside to shake out excess dust) It is very porous and holds water so when washed it takes FOREVER to dry. Also much of it washes away when you rinse it, it does not hold up well for repeated washings.” (© Jenn B of LHCOS, 2001)

****Update note**** The larger grain coral sands are harder for the hermit crab to burrow and nest in for molting. The Carib Sea sugar and select grains that are oolitic are recommended to be placed within the crabitat.

Geo-Marine: Florida Crushed Coral It’s the only crushed coral with aragonite, which provides up to 25 times the buffering power of other crushed corals, dolomite or oyster shell. Eliminate chronic pH problems and provide maximum surface area for water purifying bacteria. CaribSea’s Florida Crushed Coral with aragonite allows an increase in bioload by up to 50% and it never needs replacement! Approx 2-5mm diameter (1/8 – 1/4”).

Aragamax (Aragonite sand by Carib Sea)

Caribsea Aragonite Alive Florida Crushed Coral

CaribSea’s Arag-Alive!™

Only CaribSea’s Arag-Alive!™ Live Sands contains not just the broad spectrum of marine bacteria found in the ocean, but additional specially selected strains of marine bacteria as well. Arag-Alive!™ compresses new tank cycle time and suppresses the initial ammonia spike. Arag-Alive!™ creates a natural biological balance, and makes cycling a new aquarium faster and safer. Live rocks and most invertebrates can be added immediately. Gradually introduce fish within the first 3 weeks, and do not exceed one inch of fish per 5 gallons during this time.

Compressed Coconut Fiber Expandable Substrate

Cocofiber is often added to play sand to help retain humidity and moisture in the sand. The recommended ratio is 5 parts play sand to 1 part cocofiber.  There are a number of companies that produce coconut fiber which is sold in compressed bricks, coarse chunks or loose in a bag. Moisten with brackish water for best results.

Coconut fiber is marketed under names such as:

Substrate comparison

Quikrete Playsand

Play sand

Play sand

Poor quality sand is not recommended as substrate. Sand that is too coarse can cause harm if lodged in the shell. In some instances hermit crab owners have found metal shavings in regular sand. Always look for play sand that is intended for children’s sand boxes.

SouthDown/YardRight/Old Castle Tropical Play Sand

Play sand

Play sand

Located at:
(Hardware eg. Home Depot)
Highly prized by land hermit crab owners and aquarium enthusiasts. Unfortunately no longer sold in the United States. Now being sold to CaribSea company.

Aragamax (Aragonite sand by Carib Sea) or Aragonite by Nature’s Ocean

Natures Ocean Aragonite Sand

Natures Ocean Aragonite Sand

CaribSeas Aragamax Select

CaribSeas Aragamax Select

Located at:
Good Pet Stores and local fish stores / aquarium stores & online
Highly prized by land hermit crab owners and aquarium enthusiasts although it is much more expensive than the Tropical PlaySand.
Aragmax is an Oolitic aragonite sand from CaribSea. Another is made by the ESV Company.

Unsafe substrates

Substrates which we DO NOT recommend are: Ground walnut shells, Corn Shavings, Cedar, Wood Shavings and other reptile beddings made for desert animals. Cedar shavings should never be used as it is toxic to all animals. The oils in cedar are used in pest control because of the damage to arthropods, which would also harm your land hermit crabs. If in doubt as to the brand found locally post a message to the Forum.

Calci Sand

Hermies n herps Calcisand


Located at:
Pet Stores and local fish stores / aquarium stores and online
Not recommended for hermit crabs. Aside from being very expensive, when wet it smells terrible, clumps and sticks to the hermit crabs and then hardens like cement. Calci Sand Experiment

Hermit Crab Sand


Marketed for land hermit crabs but not suitable for the same reasons as Calci-Sand above. Comes in different colors that are unnatural and attract children.

aquarium gravel is not a suitable substrate for hermit crabs

aquarium gravel is not a suitable substrate for hermit crabs

Aquarium gravel does not allow for proper molting and may become lodged inside the hermit crab’s shell.

FourPaws Nature Bedding-made from fir shavings which are toxic due to terpenes:

Nature bed

Nature bed


Photo references:

Inland (website is no longer valid)

Stress Coat

CrabLoverDon had a wealth of information in 1999 for his time. Whereas some things have been expanded on others are outdated. To date, no ill effects have been noted from using Stress Coat, but no ill effects have been noted by not using it either. If one opts to use Stress Coat it should not be used in water that has been dechlorinated or in distilled water. Stress Coat already has a dechlorinator within it.

Below is an email on StressCoat from Crablover Don, Don Drenning, also known as CLD. This is another from an archive of messages Don sent me back in 1999 that I will be sharing with you all. Don was the first person to use StressCoat with hermit crabs and I feel it was a breakthrough in hermit crab health care. I offer it here with Don’s blessing.

Medicinal Bath for treating bacterial infections, shell rot and black spots.

This recipe can be modified, made stronger for use with very sick crabs, although this strength is fine for more minor cases!

Medicinal Bath created by Gertrude Snickelgrove and updated by Sue Latell of CoenobitaResearch and CSJ

Ingredients for Medicinal Bath for Hermit Crabs created by Gertrude Snickelgrove and updated by Sue Latell of CoenobitaResearch and CSJ

General wash for injured crabs:
1 Tbsp. Marshmallow root shaved
1 Tbsp. myrrh powder
1 Tbsp. calendula (marigold)
1 Tbsp. whole chamomile flowers (not powdered)

First, you’ll need to make a decoction. Take one quart of water, and heat it over the stove to near boiling. Add one tablespoon marshmallow root, and one tablespoon myrrh. Cover, and simmer for thirty minutes. Remove from heat. Add one tablespoon calendula flowers (marigold) and one tablespoon whole chamomile flowers. Cover immediately again. Let sit until cool, then strain herbs out and refrigerate. It will last a max of 48 hours. The herbs are all safe, they can even be fed to the crabs. I routinely feed calendula and chamomile to mine.

When bathing the crabs, bathe the affected parts only. I don’t see any need to get the stuff on the gills, unless there is an infection of the abdomen. The reason I say this, the marshmallow root makes a slime coat, which is sort of thick, and is not beneficial in the shell unless you’re fighting an infection in that area. If the infection is in on gills or soft tissue you can leave out the marshmallow root.

These are some of the general benefits of these herbs:

So marshmallow root draws out infections, draws out splinters, and makes a thick slime coat layer that helps prevent infection and aids in healing.

Myrrh powder (like what was given to Baby Jesus), is a powerful anti-bacterial, yet unlike antibiotics, is completely safe for crustaceans.

Calendula flowers (marigold), gently stimulates the immune system, is a mild anti-bacterial and anti-fungal, and cuts down on healing time.

Chamomile flowers, reduces inflammation, helps to speed healing, and reduces swelling when it is present.

A few words of caution: do not use powdered herbs; you really need to find the bulk medicinal herbs, because too many properties evaporate when the herbs are crushed. If you drink chamomile tea, and do not find it that relaxing, you should try a cup made from the whole flowers. There is a noticeable difference.

And second, all the properties of chamomile (the essential oils) evaporate with the steam. That’s why, when cooking herbs that have any essential oils, you must trap all the steam and let it cool, so the medicinal contents will remain in the formula.

Specific Wash for Bacterial Infection (including shell rot if caught in early stage):

2 cups dechlorinated water
1 Tbsp. myrrh powder
2-3 Tbsp. calendula (marigold)
1 Tbsp. whole chamomile flowers (not powdered)

Veterinarian recommendation: place the crab in clean sand, increase light exposure and bring humidity down to 70% and maintain there. Lower humidity retards the metabolic rate of the bacteria but 70% is the lowest a crab can tolerate while being treated. This must be done in isolation. Bacterial shell diseases are highly contagious but can be shed with a good molt.

This concoction should be steeped after the water is boiled. Let it sit for about 20 minutes, strain out petals. Wash should be applied 2 times a day for 3 days, let the crab sit in it as there may be lesions on his shield and abdomen. It will benefit him if he retains it as shell water. After the first few days if you notice more lesions forming or see more discolored depressions in his chitin, you may not be able to stop the progression of the disease.

If you do notice that there is no more formations, change out the substrate for new and watch him in ISO for at least another week. You can repeat the process again if you see reformation occurring. I think it would be up to you if you want to continue, but remember to keep this crab separate until you are sure that he has no active growth of the bacteria on him. With my indo BOB, he remained in a 2.5 gal ISO until he molted.

Here are his pictures:

Bob came up from his molt like this. This spot was suspected shell rot. The deformation of the claw is from an unidentified toxic substance, or even from the bacteria being present when he molted the first time.




This was after his molt and after the bath treatment. I think it contributed to him molting again so soon, and while his claw still is undercut, there was no spot or depression in his chitin.




Sorry for the poor quality of the pictures, I lost the originals when I had a hard drive crash.

Photos from Daethian:


Hermit crab with black spot shell disease

Hermit crab with black spot shell disease


Hermit crab with black spot shell disease

Hermit crab with black spot shell disease


Hermit crab with black spot shell disease

Hermit crab with black spot shell disease


Hermit crab with black spot shell disease

Hermit crab with black spot shell disease


The main recipe was given to Daethian(Stacy Griffith) via email from Gert Snicklegrove in 2005. The best of our knowledge she is the creator of this recipe along with Summer Michaelson.

The second portion is an adaptation created by Sue Latell of Coenobita Research after speaking with her vet in 2006.

Preventing death in new hermit crabs

Preventing death in new hermit crabs

Preventing death in new hermit crabs

One of the biggest concerns when buying hermit crabs is early death due to PPS or Post Purchase Stress. The term PPS has been used commonly for many, many years in the hermit crab community. PPS is blamed for unexplained deaths of new crabs. The physical stress occurs mostly PRIOR to your purchase and how many of your new crabs die unexpectedly relies on how much stress was inflicted prior to purchase. The act of harvesting and shipping hermit crabs is very stressful as the crabs are denied humidity, food, water and warmth for long periods prior to shipping and during shipping. They mostly arrive at pet stores dry, hungry, dehydrated and sometimes cold. The last crabs harvested before shipping will be less stressed and more likely to survive. Naturally the opposite holds true for the first crabs to be harvested. Often it takes a period of time for the stress and dehydration to catch up with them but it does and the hermit crab dies. Sometimes it’s a week, or a month but it could take longer. Gill damage from dry air (lack of humidity) can be a slow painful death for a hermit crab.

There are some ways to give your new pet hermit crab the best possible chance at survival. When you purchase new crabs, take note of the store conditions. If there are no gauges, do your best to guess the humidity. When you bring home a new hermit crab, place it in an isolation tank with the same humidity as the store. Use a tiny amount of moss if needed to create the proper humidity. The temperature should be at 72F and remain there. Place a very small amount of sand in the tank, not enough for the crabs to burrow in. Leave the crabs alone except to change food and water. This will allow the crab to relax, destress and get enough to eat and drink. It is very important that your crabs eat well during this time. Food fuels metabolism and this is how they will adjust to the tank settings as you change them. Once you have a consist starting humidity at or near that of the store, hold it there for four days. In four days, add some more moss to bring the humidity up 5%. Continue to increase in this manner until your ISO tank is the same humidity as your main tank. Between the 3rd and 4th week, add more sand so that the crabs can dig down if they want.

If you buy more than one crab, it is okay to place them in the same isolation tank together.

It’s a good idea to closely inspect the hermit crabs before placing them in your main tank. Look for signs of mites or black spots on the exoskeleton. If the hermit crabs have mites (parasites) or black spots on the body, you should keep them quarantined until the mites are gone or they have molted and the black spots are gone. Shell disease is contagious.

If you adopt or purchase hermit crabs from a filthy environment where bugs, flies, maggots are present you should prepare a SHALLOW tray of dechlorinated water and place the crabs right side up and let them walk around. The water should only be deep enough to touch the lower lip of the shell…this will allow some water to swish in the shell and hopefully wash out any parasites or fly larvae. This is really a worst case scenario that we don’t often see but it does happen. If you are rescuing hermit crabs from these conditions be prepared to keep them isolated until you are 100% sure they are free of parasitic mites or other bugs. You do not want to introduce these things into your established tank and hermit crab colony.

Bathing your hermit crabs as a matter of routine is strongly discouraged.

Sue Latell of has put together two articles on reducing the impact of PPS in newly purchased crabs. Members of The Crab Street Journal helped conduct the trials on this method and did report a definite change in the death rate of newly purchased crabs. The two articles are linked to each other and also explain the importance of having lights for your crabitat. These are MUST READ articles because they cover a lot of important information.

Refining the Purpose of ISOLATION

PPS (Post Purchase Stress): Minimizing the Impact

This information is based on the exclusive research of Susan Latell, All Rights Reserved.

More articles about PPS:
PPS Minimizing the Impact
Technique for Adjusting PPS Crabs
Comparative Example for PPS Practices
Preventing Death in New Hermit Crabs

Pre Molt Symptoms

Coenobita perlatus digging

Coenobita perlatus digging

Observed Premolt Symptoms

by Marie (aka ladybug15057)

At times, crabbers become concerned due to certain actions their hermit crabs are beginning to display. Often, they are concerned that the hermit crab is ill, or has another form of complication happening that needs attention. Where, as on occasions, the symptoms they are observing may be due to a stressful situation, whether it be from their past or current living conditions, there are many times that the hermit crab is displaying premolt symptoms. If one knows that he/she has provided the hermit crab with the essentials it needs to thrive (proper humidity level, proper temperature, proper diet, bacteria/mold and a pest-free environment, etc.), what you are beginning to observe may very well be premolt symptoms that the hermit crab is displaying. With the numerous molts we have had, I would like to share some of the premolt symptoms I have observed with our hermit crabs and hope it can be of some help to ease other crabbers concerns.

Please note that not all hermit crabs will display premolt symptoms prior to molting. Some will do a surprise molt displaying no symptoms, but here are some we have noted with our hermit crabs:

1. Gorging food for almost 2 weeks prior to molting.

C. variabilis eating avocado byLisa Dawson Dec 2015

C. variabilis eating avocado by Lisa Dawson Dec 2015

2. A few days–up to and including almost 2 weeks prior to molting–consuming no food at all.

3. Very restless behavior during the daylight and evening hours, including attempting to climb the glass walls inside of the crabitat as though they are looking for a way out.

4. Dragging their large cheliped almost under them as though it is too heavy to hold up, or in front of them as opposed to being slightly in front of them when they are scooting.

5. The V shaped eye stalks _/ as opposed to the typical parallel eye stalk shape. |_| The pupil of the eye stalk looks as though they are looking outward as opposed to straight ahead.

6. Eye stalks in a downward position as opposed to a standing up type position. When the eye stalks are in this position, this means that the hermit crab is very close to molting, or has already begun the actual molting process to remove its exoskeleton. By no means at this time should the hermit crab be disturbed in any way. By doing so, this could be lethal for the hermit crab.

Hermit crab pre molt eyes

Hermit crab pre molt eyes

7. The leg tips of the hermit crab turn lighter in color, along with a lighter whitish/beige coloring at the joints of the legs and the chelipeds. With some, the outer parts of the legs change to a whitish/beige in color with the very center of the legs and chelipeds having a darker coloring to them.

Hermit crab pre molt

Hermit crab pre molt

8. Along with the lighter coloring of the hermit crab’s exoskeleton, if one looks closely where the joints meet, you can at times see where the old exoskeleton is pulling away from the new body. When this happens, the new body underneath can be seen. This reminds me of when a human wears pants, and sits on a chair. You can see the ends of the pants, and usually the socks underneath.

9. When the hermit crab is scooting through the sand in the crabitat, its shell leaves a deep groove type impression in the sand. This dragging of the shell can also be observed when the hermit crab is out of the crabitat in a drip dry area where the shell being dragged along the bottom of the area can actually be heard.

10. When the hermit crab is scooting, its legs are out to their sides as opposed to being in an upright hermit crab style curve when walking. (This reminds me of the stepped-on bug effect look.)

11. When the hermit crab is picked up and it first comes partly out of its shell, one of its front legs stick straight out as though it has no control of it. Within a few seconds, the leg goes into a normal position like the other legs.

12. The premolter spends a lot more time than usual in, or around, the water ponds. This behavior has been observed around the ocean water pond as well as the fresh water pond. With our hermit crabs, it is observed that they frequent the ocean pond more than usual, and the ocean pond will need refilling a few times a day.

Coenobita perlatus submerged in water

Coenobita perlatus submerged in water

13. Some of the hermit crabs get an odor to them. This odor reminds me of the silicone that is put around a tub/shower. Some crabbers have related this odor to iodine, or butterscotch.

14. The hermit crab will attempt to find a secluded area away from its tank mates. Many will go into single hidey areas we have within our crabitats. Smaller hermit crabs have gone into larger extra shells–in their own shells– where they can hide. This reminds me of a shell plug within the larger shell opening.

15. The hermit crab has slow antenna movement and appears lethargic, or depressed. Unless they are picked up and moved, they remain in the same place they were put.

16. A behavior change is noted. A very shy, out-going hermit crab appears shy, or withdrawn. It is scooting about the tank most of the day as if in search of something. It becomes slightly or overly crabby with its tank mates. I have one hermit crab that never digs, but when in premolt she will begin to burrow.

17. The hermit crab appears to suddenly become uncomfortable with the shell it is wearing. It begins to change shells frequently, but just cannot seem to find that right fit regardless of what shell it has on. This behavior is more frequent than a normal hermit crab trying shells on for fun or entertainment.

Hermit Crab Shell shopping

Hermit Crab Shell shopping

18. The hermit crab will begin to dampen or wet the sand regardless of how perfect the humidity level is at the time.

19. The hermit crab will begin to remain about half way out of its shell when it is relaxing, as opposed to being mostly within its shell.

20. The hermit crab will have whitish, cloudy or hazy looking eyes. I have also observed the pupils of the eyes being a dull reddish brown in color as opposed to being the bright, shiny, almost black color.

Hermit crab pre molt eyes

Hermit crab pre molt eyes

21. With some of our hermit crabs, it has been their tank mates that let me know that they are in premolt. It would appear that the premolter is all of a sudden a very popular hermit crab. His/her tank mates will surround him/her, or block the entrance to the single hidey that it has chosen to try to seclude itself in. The tank mates stay next to him as though they were best buddies, or trying to protect his friend. (Mating takes place prior to molt and this could explain the unusual interest in the molter)

Antennae war

Antennae war

22. A water sac is observed on the hermit crab?s side within the shell. (This may not always be observed.)

Pre molt water sac

Pre molt water sac

Pre molt water sac

Pre molt water sac

23. If the hermit crab is missing a leg or cheliped, a gel limb will form. The gel limb appears to go through a sudden growth spurt the closer the hermit crab is to actually molting.

Gel limb big pincher regenerating by Lamont Darren Medley

Gel limb big pincher regenerating by Lamont Darren Medley

When I observe any of the behaviors mentioned above, I isolate the hermit crab from his tank mates for its own safety. I have found these to be premolt symptoms with our hermit crabs. This is not to say there are not other premolt symptoms that I have not included in this list, there very well could be, but these are some of the ones I have observed.

If any of these symptoms are noted on your hermit crabs, please act accordingly. It is not always true that a hermit crab will burrow to molt. To date, we have 82 hermit crabs and I have had 319 molts. All of our hermit crabs, C. Brevimanus, (Indos), C. Rugosus, (Rugs), C. Clypeatus, (PPs), C. Compressus, (Es), have molted above substrate without any attempts of trying to burrow, except for the one Ecuadorian who will begin to burrow when she is in premolt, and will molt within a bottle once she is in isolation. Of the 82 hermit crabs we have, I have four C. Prelates (Strawberry), hermit crabs that have lived with me for over a month and have not yet molted.

(Edited 2/1/2010) I had written this original article about December of 2004. Since then all 4 of my Strawberry’s have molted several times. An observation I have made is that they appear to spend prolonged period of time in the ocean pond prior to molting. I have observed them almost completely submerged up to about 20 minutes at a time.

Photo Credits:
Marie Davis
Michelle Stephen
Stacy Griffith
Lisa Dawson
Lamont Darren Medley