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Hermit Crab Molt: What To Expect

A healthy hermit crab will go through several molts throughout its life. Crabs, insects, and even spiders have to shed their outer hard exoskeleton to grow bigger. The outer casing doesn’t expand, so in order to grow, these animals have to molt.

For hermit crabs, this process will only happen if the setup in the tank is precisely right. It’s also an extremely stressful and vulnerable time for your hermit crab. If it is disturbed or over stressed during the molting process, it could cause the crab harm or even result in death. 

A successful hermit crab molt doesn’t have to be stressful for the crab or you as long as the right conditions are met. In this article, we will explain the entire process, how long it takes, and what you can do as an attentive and caring hermit crab caretaker. Come on, let’s learn all about hermit crab molting.

All About Hermit Crabs During Molting

Freshly molted crab by Maru-Sha
Freshly molted crab by Maru-Sha

As stressful as molting can be, it’s really not a hard process, and there’s not much you need to do. Hermit crabs know when they need to break out of their shells, they know how to manage it correctly and don’t need any help. 

The most important thing you can do is make sure your pets have the correct amount of substrate in the enclosure, make sure it’s humid enough, and then leave them alone as they go through the process. 

Hermit crabs—depending on how large they are—need about 6 inches of soft, damp soil and sand in which to burrow. The depth depends on how big your hermit crab is. A general rule of thumb is to have around 3 times the depth as the crab is tall. 

For instance, if your hermit crab is only one inch tall, you need about 3 inches of substrate. A 2-inch hermit crab needs about 6 inches of substrate and so on. The soil also needs to be damp enough to stick together and not crumble when your hermit digs a tunnel.

How Often Will My Hermit Crab Molt?

There’s no magic number to how often your hermie will molt. When they need to and have a proper enclosure, they will molt. 

Younger hermit crabs are growing a lot, so they have to molt more often. Since they are smaller, it may not take as long to go through the entire process as a large, tennis ball sized hermit crab.

Juvenile hermit crabs could molt as often as 3 to 4 times a month and could take between 2 to 4 weeks to complete the process. Medium sized to jumbo hermit crabs will not molt as often because they aren’t growing as fast. Larger hermit crabs could go through the process between every 6 to 18 months.

How Long Does The Molting Process Take?

Hermit crab molting is a long process. Some owners may wonder if their pet dug a hole and then passed away inside. When a hermit crab goes into hiding and stays there for a month or longer you may really wonder, I certainly would.

You’ll just have to be patient and not bother it at all. You’ll know by the smell if your pet is still molting or has moved on to the next stage in life. As long as you don’t smell something foul and rotten, your crab is doing fine.

A typical hermit crab molting process takes about 4 to 8 weeks. That’s right, it could be in the hole for as long as two months. 

Signs Leading Up To Molting

There are some subtle clues your pet will give off when it’s nearing molt time. They may start digging a lot more. They will especially dig more often if the substrate isn’t deep enough or is too crumbly. 

They need a sand and soil mixture with enough moisture for it to hold the shape, so the tunnel doesn’t fall in while they are molting.

More Time Soaking

Another indication they are about to molt is they will spend a lot more time soaking, especially in the saltwater container. Hermit crabs will store moisture and salts in their body to prepare for the molting process. 

They use the water to increase pressure under their shell and to help split it open. If you can see the underside of your hermit crab, you may notice a bluish-black addition on the abdomen. This is where they store water and food for the long molting process. 

Moving Into A Smaller Shell

That’s right, a smaller shell instead of a larger one. This is because they know a large shell will be harder to carry into the burrow with them. It could also collect more dirt and sand while it’s digging, and besides, the hermit crab will be slightly smaller right after the molt.

When you see your hermit crab trying on smaller shells, it may be time for a molt.

Cloudy Eyes

If you have owned snakes, or have seen them just before they shed their skin, you’ll see something similar on your hermit crab. Their eyes could be cloudy and their shell may look dull or chalky.

Once the exoskeleton has been shed and replaced, the new shell will be more vibrant and sharper looking. 

Decreased Activity

Shedding an exoskeleton is hard, exhausting work. Your hermit may not be as active as usual, instead of running around, it may be resting to prepare for the molting process. 

Preparing Your Hermit For The Molt

So you’ve noticed the signs and are sure that your pet is about to go through the molting process, what should you do to help it out? To help prepare for this exhausting experience, you can feed your hermit crabs a diet higher in protein and calcium to help prepare. 

Make sure there is enough fresh and saltwater for your hermit crab to completely submerge itself, shell and all. It needs extra water to separate the soft shell underneath and crack open the old exoskeleton. 

Lastly, you need to make sure you maintain humidity levels at 70 to 80%. You could mist the substrate around the hole just to make sure there is enough moisture for the process. 

Don’t disturb your molting hermit crab. Digging it up or opening up the substrate to see what’s going on in there could cause harm or even be fatal to the hermit crab. They are very soft and vulnerable during this time. 

Some people recommend moving the molting crab to a separate tank, especially if you have multiple crabs in an enclosure, but this could stress the molting crab, and isn’t necessary. Hermit crabs have been molting with others around way before they were pets.

If you feel you need to separate your hermit crabs, a divider that your hermits can climb is a better option than trying to move one. 

It’s Molting Time

Hermit crabs will produce a hormone that tells them it’s time to molt. But, if the substrate isn’t deep enough or the process gets delayed in any other way, they will secrete another hormone that delays the molting process. They can keep putting the molt off until they die if their needs are not met. 

This is one of the reasons beachside cages with no substrate at all are so bad for hermit crabs.

What Are They Doing In The Burrow?

Once the hermit crab has dug a hole and is now ready to exit the old skin they will use the water they stored to separate the new, soft shell from the old. Then they crack it open using the same hydrostatic pressure.

Next, they remove themselves from the old shell. This is when they are the most vulnerable. They have very little protection, and they actually produce a smell that is attractive to other hermit crabs. 

I’m sure this is one of the reasons they bury themselves and want to be left alone. 

During this next step, the hermit crab consumes the old shell. They need the extra calcium and minerals in the old shell to help harden the new exoskeleton. This process takes the longest. 

Finally, the hermit crab rests while the shell bulks up and hardens, and once it is finished, the hermit crab will emerge. You’ll see new “hairs,” or setae all over, the shell will be polished and vibrant, and their claws are sharp and pointy.

If they have lost any limbs or claws, the appendage will start to grow back. You may even notice a slight, jelly-like nub growing where the lost limb is. In a matter of a few molts, a new leg or claw will be completely reformed.

After The Molt

Be very careful with your newly molted hermit crab. Don’t mist it, don’t try to pick it up, just leave it alone and let the new exoskeleton harden. The new outer covering should be hardened when they emerge, but be aware that it may be slightly pliable.

After this stressful time period of limited food and water, be sure to provide plenty of clean fresh, and saltwater to drink and soak in. Also, feed a high protein and high calcium diet to help replenish what was lost during the molt. 

If you don’t already, now is a great time to offer a large selection of new shells. Some hermit crabs take on a smaller shell just before they molt and will now need a larger one since the exoskeleton has hardened and bulked up.

Once your crab is regularly active again, alert, and moving around like it was premolt, you can handle it like you used to. 


Do hermit crabs molt on the surface of the substrate?

Surface molting can happen, but it’s a rare occurrence. If you see this happening, don’t worry, simply allow the molt to happen naturally. If you have an enclosure with more than one hermit crab, you may need to protect the molting hermie.

Hermit crabs might try to eat the exoskeleton of the molting crab, or they could turn savage and try to eat the soft, vulnerable crab. This is natural in the wild and it’s one of the reasons hermit crabs will burrow to and hide away during this stage.

You can put in a divider to separate the molting crab and other crabs. If you don’t have a divider or need something in a pinch you could use a clean, empty soda bottle, a large plastic bowl, or some other container to place over the hermit crab.

In the case of the soda bottle, cut the bottom off, and take the lid off to allow air circulation. Then place it over the molting crab and press the bottle into the substrate so it won’t fall over and other crabs can’t accidentally knock it over.

You can do the same with a bowl or other container as long as you poke a few small holes in it for air and humidity circulation. 

Do hermit crabs stay in their shell while molting?

Hermit crabs do tend to stay in their shell during the molting process. This gives the crab extra protection and helps to “mold” the soft crab into shape. While they are in the shell, they will consume their shed exoskeleton to replenish lost calcium and minerals.

They need these extra minerals to harden off the soft, new exoskeleton.

Will other hermit crabs eat a molting hermit?

Molting hermit crabs produce a scent that can attract non-molting hermit crabs, and may cause them to want to eat the soft, molter. Hermit crabs are scavengers and will eat dead crabs, but rarely will they attack another crab with the sole purpose of consuming it, except during the molt.

This is one of the main reasons it’s imperative to have a thick substrate that allows for burrowing. Tunneling into the substrate will mask the molt odor.

By providing plenty of protein for your other hermit crabs, you’ll help protect your molter. Sardines, shrimp, oysters, fresh fish of any kind, boiled eggs, chicken, insects, and beef all are acceptable protein sources for hermit crabs. Provide some type of meat with vegetables, grains, and fruits for a balanced diet for your hermit crabs.

Wrapping It All Up

Molting is a natural process that all hermit crabs go through. We as humans want to take care of our animals, and sometimes we feel we aren’t doing enough, especially when our beloved pet starts going through a stressful process.

When it comes to molting, there’s really not much we can do to help these tiny critters. In fact, doing less is doing so much more. Just make sure they have enough substrate to stay covered and safe. Keep the humidity high, and be patient.

After you go through the molting process with your hermit crab a few times, you’ll know exactly what to do, and what to expect. We hope this article answered your questions about hermit crab molting, and if you learned something and enjoyed it, please leave us a comment below.

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