New Molt. Look behind the old skin and you'll see the new claw of the actual crab!
Molting Demystified!
Clues that the miracle of molting is near:
There are a lot of little signs that a hermit crab gives its owner before it needs to molt (shed its skin). This page details most of them, and describes how to set up an isolation tank so your crab makes it through this difficult time.
If your hermit crab has just molted and you are looking for immediate help, please scroll down to the Surprise! section.New Molt. Look behind the old skin and you'll see the new claw of the actual crab! |
Crabbie is digging! An otherwise healthy crab that is suddenly overcome with an urge to dig is your first clue that a molt might be on the way. Before you assume this, however, check your trusty thermometer and humidity gauge. A tank that is too warm, cold or dry could cause your crab to dig himself a little "microhabitat" under the sand where he is insulated from conditions he does not like. Newly purchased crabs in particular are prone to dig into the substrate for a while. Sometimes they do this only because they want to rest, and sometimes it is because they are indeed molting. Pet store conditions are rarely optimal for a molt, so if your new crab digs in, leave him alone. It might be hard for you to do, because you just got your new pet and you want to get to know him. However it is best for him (and for you in the long run) if you let him acclimate to his surroundings on HIS time. Smooth
out the sand over and around him Then if he decides to pop up at night for
a drink or a bite to eat, you'll know that he is only destressing, and probably not molting. The FAQ page contains this info and more about digging crabs, and explains what to do about certain behavior.
Is Crabbie drinking or eating a lot? A molt might be on the
way, but first, let's look for some other clues. Molting hermit
crabs have a two-pronged strategy for molting: 1) store up a lot of fat and
water and 2) get So what is this "Molting
Isolation Tank" like? The molting isolation tank (or "ISO"
for short) is where your crabs go to molt in safety and privacy. Ideally it
is filled with at least six inches of soft, moist sand. The sand should be moist
enough to make a sand castle, but not so moist that it is drippy. The
tank should be large enough to hold food and water dishes. To make my
ISO, I purchased a 10 gallon aquarium from PETsMART for less than $10 and outfitted
it with an undertank heater and a glass lid. The substrate is the easy
part -- use sand. Gravel (except very fine-grade gravel) is too coarse;
crushed coral and Calci-Sand® are too organic and spoil when moist. Play
sand is the best molting substrate, because it is inexpensive comes in a nice
big bag. For a good ISO tank, you will end up using most of your play
sand, believe it or not! Fill your tank with about six inches of
the play sand. Then take a jug of water and pour about one cup of water
into the sand. Mix it up very well and note how moist the sand is.
Can you make a little circle in the sand with your finger without the sides
caving in? That is what you are aiming for -- a substrate that is moist
enough that you can make a little hole like that, which is what you will do
for your crabs when they need to molt. Start out with only one cup of
water and if necessary continue adding water until your sand is moist and packable, but not watery or drippy. Once you get that right, you are over the hardest
part. Next, add your food and water dishes. "Molting food" should be something that
is rich in calcium, like cuttlebone, sand dollars, sea biscuits, or Calci-Sand®.
For water, give the crabs their regular dechlorinated drinking water. I usually
add a bit of saline water to the regular water, because molters need the extra
salt to help retain water. You may or may not want to put some big shells into
the ISO tank, just in case you have a crab that is doing a "last minute" molt
and he/she needs a dark place to do it ASAP. Some crabs will be far along in their pre-molt preparations when you find them, and therefore might not have enough time to dig deeply enough into the sand. They will go "face first" into a large shell and molt there. The finished ISO tank should look a bit bare in
comparison to the crab's "living quarters," and rightfully so. After all, the
crab is not using this ISO tank to climb around and play in, but for the very
serious business of molting. Molting is how the crab grows; since he lives inside
a hard outer casing, he cannot grow larger except in the short time while his
exoskeleton is soft, namely, directly after completing his molt and before his
skin hardens up. Darkness is your friend Indeed it is! Studies have shown that hermit crabs have two molt-related hormones that enable them to 1) put off molting when the conditions aren't right, and 2) to get down to business when they are!
The molt-inhibiting hormone can put into play by numerous factors, but the most
important one for hermit crab owners to remember is that hermit crabs have been shown to have better, healthier molts when they are under the substrate, or
in complete darkness. This is why if your molters have not been able to dig,
why they will molt inside the mouths of larger shells or under tank ornaments.
"Each stalked eye of a decapod crustacean contains some of the neurosecretory
cells that synthesize and release molt-inhibiting hormone." (Shrimps Lobsters
and Crabs: Their Fascinating Life Story,Dorothy E. Bliss) The good news
is that hermit crabs also have the molting hormone Crustecdysone to help them along when conditions are right. If your ISO tank is set up correctly,
when you notice the pre-molt symptoms (affectionately referred to as "PMS") in your crabs, get them into your ISO set up right away.
Preparing for the Big Event!
Here is my usual procedure for checking for molters. Each day I check on my
hermit crabs, and I notice who is digging, who is drinking, eating, etc. When a crab has been attempting to dig a lot, I remove him and examine him for molting signs. Then if I think he may be wanting to molt, I give him a bath in StressCoat®-treated water. When I bathe most of my crabs, I will tip the crab up on its side and drain out the excess water. Not so with molters. The crabs going
into my ISO tank go in there with a shell of water.
When I am at the ISO tank with the
molter in my hand, I open the tank and use my finger to swirl a little circular
hole into the sand that about as large as the crab. Then I set the crab into
the hole. A crab that is truly interested only in molting will dig in and be
completely vanished under the substrate in about 1/2 hour. Check on your ISO
tank and make sure your crab is dug in. If he is not digging then he may need
a protective shield put around him because he is weak or going to molt immediately.
An excellent temporary molting shelter for surprise molts is the top half of
a 2-liter soda bottle. Take off the bottle cap and discard it. Wash out the
bottle well with plain water, dry it and push it into the substrate around the
molting crab. Be sure you push it in as far as it will go -- hermit crabs have
been known to attempt to dig it up to get at the molting crab. If you use the soda bottle method you might want to put a dark cloth over your crabitat so similate the darkness the crab needs to molt successfully. Cleaning your Isolation Tank.
You might think that the Isolation Tank will get dirty over time, what with
all the crabs that use it. On the contrary, the isolation tank is the cleanest
crabitat there is! Crabs that are molting are not concerned with food and
digestion. Before they molt, they store up food and water. Once they are under
the sand, they live on their internal storage. Once they complete shedding,
they eat their exoskeleton and, because all nutrients from the exoskeleton are
absorbed, the a crab eating its exoskeleton does not produce the amount of feces
that an un-molting crab produces. Cleaning your isolation tank should be done
at a time when there are no crabs in it. You clean the tank when you remove
extra exoskeleton pieces left behind by crabs that weren't interested. Every
three months or so, you stir up the sand (bring the bottom sand up to the top)
and add a bit more water to keep the "sand castle" consistency.
Surprise!
One day you pick up your crab and he falls out of his shell! He was just moving
around on bath day, what is wrong? In this case, molting is probably the culprit.
Unless there is a strong fishy odor the crab is more than likely not
dead. Note that freshly molted crabs also have an odor, but it is different
from and not nearly as strong as the ‘death smell.’ It smells more like epoxy
or iodine. A molting crab may appear to be dead, however --the exoskeleton falls
from the shell as if the crab has died. Check -- no reeking smell? Check the
home shell. You probably have a newly molted hermit crab. You can also see if
the discard is hollow or crumbles when you squeeze it.
"Sneaking peeks." Molting is very stressful for the crab. The
BEST thing you can do for [a molting crab] is leave it alone! One spritz of
water a day in the molter's area is the most attention he should receive, and even then you should not pick him up. He needs to be left alone so he can start to
regain some energy and to allow the new exo to harden. Make sure the area you
have him in is warm, and quiet and away from active areas of the house. Check
in on him occasionally by looking at him but do not handle him or try to help
him with his molt. Hermit crabs molt in the wild all the time and they know
what to do. Please do not complicate matters by trying to serve as a nursemaid.
Pulling on his little body could seriously damage him and result in him losing
appendages if he has not completed his molt. If you MUST transport him, gently
use a spoon to lift him, shell, exo and all and place him carefully into the
new place. At this time their new exoskeleton must harden and they are very
vulnerable. As little disruption as possible is necessary, thus it is recommended
that you isolate the molter from the others by blocking off an area of isolation
for him or transporting others to another area so he is not disturbed. One way of doing this without moving the molter is by setting up a temporary molting shelter.The more
secure he feels the more readily he will be up and about. When isolating a molter,
have a small amount of water close by if they wish to partake. Molting is stressful
for the crabs; their new exoskeleton must harden as they are vulnerable at this
point. As little disruption as possible is necessary, that is why the immediate
isolation from other crabs is highly recommended. A note about cannibalism:
For some reason, land hermit crabs find the smell of freshly-shed exoskeleton
irresistable. They will attempt to climb over and/or tunnel under most isolating
devices. Because of this, you should make every effort to remove the molter
to a separate tank as soon as possible. If this is not feasible, the soda-bottle
method will work, provided the substrate is very deep. Don't rely on home-made
partitions to keep the crabs separate -- they will scale the partitions and
the results will be devastating. So for the safety of the crabs, isolate them
at the first sign of an impending molt Killed with kindness. Please
refrain from bathing the crab while he or she is still soft. Moisture is good
for a molting crab, but too much moisture can harm a molting crab by encouraging
the growth of mold or flesh-eating bacteria. If your crab is struggling to shed
its skin, you can give it one or two quick spritzes from a mister, but do not mist
the crab until it is sopping. If you have any questions about how to prepare
FOR a molt, do it ahead of time. Before you decide that you have to do this or that, back up your urge with facts. Do your homework so your crabs don't suffer the consequences. I've Had My Crab for 10 Months.
Why Hasn't He Molted? Most healthy crabs molt at least once every 18
months. SOMETIMES smaller crabs molt more frequently, but not always. So don't
worry if it's been a year and your crab hasn't molted yet. Just continue to
take good care of it, and the crab will molt when it is time. In the interim,
I suggest that you read up on all that you can find on molting. There are really
no black and white 'textbook procedures,' but some very enlightening observations
out there. During an average molt a hermit crab will not come out of his seashell. But What About The Leftover Skin? Believe it or not, the crab
(after its claws have adequately hardened) will eat its old skin. The ‘old’
skin is full of nutrients such as calcium and especially the important skin-hardening
agent chitin. In a regular molt, it often takes day a day or two for
a crab to rest and its claws to harden before it regains the energy to eat its
exo. Most of mine wait a couple days, but there are those few exceptions that
are molted and finished eating the exoskeleton before you realize anything has
happened! Pieces of the exoskeleton that are not eaten by the molter should
be recycled into the ISO main food dish as an extra source of calcium and chitin.
I use a coffee grinder to grind up what the crab leaves behind. Some crab owners
crush their crab's exoskeleton because they believe it makes it easier for the
crab to eat. However I believe that the exo should be left intact -- the crab
knows which parts of his exo he will need to eat first, and crushing it all
together is not necessary. Size Matters It has been my experience that larger crabs take
a great deal longer to complete their molts. In particular, a bigger crab will
rest a couple days before even beginning to eat the exoskeleton. Larger crabs
are more likely to be stressed since they molt less frequently. Of course, there
are those exceptions. The best advice is to allow nature to take its course
- let your jumbo do what he has to do and leave him be! He has molted for many
years already and you do not need to constantly check on him. If a large molter
has a good-sized "water bubble" stored up and the exo to munch on,
then he really has no need to move much. The average amount of time for a crab
baseball-sized and over is one full month under the sand. Crabs that have everything
at their disposal and the proper set up to dig down while in pre-molt will take
up to six weeks to prepare, AND they will have a better chance of surviving.
Remember, to dig up a molter is to kill it with kindness. Let Mother Nature
play her part in your crabs' lives. A smaller crab can still take up to a month,
depending on whether or not the crab has a lot of regenerating to do, or if
it was adequately prepared to molt. On the other hand, I've personally had teeny
crabs (the size of 4Ts in the Happy Hermit Photo Album)
molt and be ready to rejoin the group in about three days. So size does play
a very big part in whether or not your crabs' molt will be successful. Everyone's Crabs Are Molting But Mine! A lot of people report
that their crabs seem to want to molt at the same time. This phenomena appears
to be unique to each owner, so while your crabs might be flipping exoskeletons
like mad, your neighbor might have hermies that aren't the slightest bit interested
in molting. So there is no need to stress yourself and wait for it to happen
because you heard there is a 'season' or that you had that crab for this or
that period of time! 
underground to molt. So before your crab goes shell-up and heads for the bottom of his crabitat, he may eat and drink like you've never seen before. The confusing part of it is that he will probably do all his "tanking up" at night after you've
gone to bed. But all his eating and drinking usually adds up to one very important clue that his molt is coming up! Before a molt, a crab will store extra fat and water in a small blackish "bubble" that is usually on the left-hand side of the abdomen,
just under the fifth pair of legs. The picture to the right shows where to look
for the black molting "bubble." You might have to look hard, because this little
crabby "spare tire" is gelatinous and may spread out under the crab. Do
not, however, assume that a crab is molting just because he is showing this
bubble. Always look for the other molting signs,
such as: general lethargy, less antennae activity, tangled and confused-looking
antennae and an ashy exoskeleton or dull-look of their eyes (like a cataract
on a human).
A crab that is missing limbs and is nearing a molt will begin the process of regenerating its limbs. The area where the limb is damaged will appear to grow a small nub that looks like clear gel. This is actually the limb encased in a clear chitin sheath. As time goes by and the time for molting grows near, the crab's gel limb will swell and become more defined. 
Isolation (ISO) unit with
deep sand for crabs to hide in. Water dish is to left (above burrowing crab).
Black calci-sand provides calcium for growing crabs.
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