What Is Hermit Crab Molting: Understanding a Hermit Crab’s Molting Phase

Molting is the process of a hermit crab shedding its exoskeleton. This natural process happens every 18 months, essential for the hermit crab’s health. During molting, the hermit crab sheds its old hard shell and replaces it with a new soft exoskeleton. 

Molting is a natural process that hermit crabs go through to grow and get bigger. It usually happens halfway through the crab’s life and lasts about four to eight weeks. 

Types of Hermit Crab Molting

The molting process depends on the crab’s environment and size and can occur in several ways. Once the molting is complete, your hermit crab will look its best! Keep an eye out for new molting exoskeleton shells as they will start showing up around your hermit crab’s enclosure. 

Underground Molting

Hermit crabs are exciting creatures that go through a molting process every few months. This process, known as mid-molting, involves the withdrawal of the old epidermis and the introduction of a new one underneath it. The molting happens in three stages – pre-molt, mid-molt, and post-molt. 

During the pre-molt stage, the crab retracts its legs and abdomen into its shell. Later on, during the middle molting phase (post-molt and mid- molting), hermit crabs exude seawater from their eyes, anus, and cloaca (the opening leading to reproductive organs). Lastly, during the final stage of midmolting (between post-molts), they release water from all over their body, including their claws and antennae.

Surface Molting

Surface molting is a crucial part of the hermit crab life cycle and helps the crabs adjust to new habitats or climates. However, it can be pretty traumatic for some hermit crabs. Thankfully, most hermit crabs get over it fairly quickly and return to their usual antics soon after undergoing this process.

Isolation During Molting

During molting, a hermit crab will become isolationist from the rest of its colony to focus on healing without any distractions.

Signs That Your Hermit Crab Is Molting

During molting, your crab will likely change its behavior – it may become more active and climb on things high up. Keep an eye out for noticeable changes in appearance, as molting can cause your crab to shed its exoskeleton. 

If you see anything suspicious during this time, contact a hermit crab expert for advice. In the worst-case scenario, molting can be fatal for your crab, so it’s essential to monitor it closely.

Increased Appetite

The molting process can cause your hermit crab to increase its appetite and lose weight. If you notice any of the following signs, it’s best to take your crab to a vet for treatment: clustering around the food bowl, eating more than usual, losing weight.


The process of digging is an essential part of hermit crab life. It usually lasts around two weeks, and your crab will become much more active. Look for the signs that it’s digging – increased appetite, changes in coloration, etc. If you see your crab digging in its shell, it’s time for molting!

Change in Color

It’s natural for crabs to change their color over time. This process can start a few days after the crab has molted and ends within a couple of weeks. 

Keep an eye on it, make sure it is safe for you to touch, and don’t be alarmed if your crab starts losing its color – this is just part of the natural cycle! If your hermit crab shows any signs of distress (e.g., refusing food or water), immediately take it to a vet.

Regeneration of Limbs

Regeneration happens in the crab world every so often. The process usually takes around four to eight weeks to complete; during that time, the crab is quite vulnerable. 

If you want to speed up the process, you can help your crab by providing suitable habitat and avoiding intense light. Hermit crabs have a rigorous molting schedule and can be pretty picky about it. You will see your crab walking around more, eating more, and generally looking much healthier!


Molting is a stressful process for hermit crabs; if not done correctly, it can lead to death. Thankfully, molting isn’t too painful for them – in fact, most of the time, they come back looking just like before!

Make sure you keep your crab calm and isolated from other crabs during the process – this way, they won’t have to compete or fight for resources and will stay healthy overall. 

Signs of Incoming Molting (Pre-molt Phase)

Difference in Behavior

Keep an eye out for your hermit crab’s behavior. If it becomes restless, eats less, or vomits up old shell material, there may be trouble ahead. Action accordingly by providing support and care until the crab is ready to molt again. 

The hermit crab will start hiding away from its shell more often as well – this is normal behavior during molting and indicates that everything is going according to plan!

Difference in Appearance

The molting process is a significant transition for hermit crabs, and the transformation can be quite visible. Apart from changes in their carapace (upper shell), pre-molt hermit crabs will also have more rounded shells than post-molt crabs. The difference in appearance can be so dramatic that it’s easy to mistake one crab for the other! 

Another noticeable sign of molting is when hermit crab shells become duller in color – this signifies that the crab is preparing to molt into its next exoskeleton shell.

Limb Regeneration

During molting, the crab may change its coloration and reduce its food intake. The abdomen will shrink dramatically – this is where new legs will grow! Gradually, the crab becomes more active and mobile around its shell over days or weeks. 

What to Do if Your Hermit Crab Is Molting

A hermit crab molting process can be confusing, but watching the crab is essential. Provide fresh water and food as usual. Keep an eye out for dark patches on the shells.

Ensure the crabs have a secure place to reside while molting (a clean tank with few rocks will work). Please do not touch or handle the crabs during this time; it can cause them stress and make the process more difficult. 

Setting Up an Isolation Tank

It’s essential to set up an isolation tank for the crab so it can adequately molt. The water temperature, humidity levels, and the substrate should be adjusted to provide the hermit crab with the best environment for the molting process. 

You can buy another tank and have them move over, or place them into their new home and turn off the light until morning. If you’re feeling creative, you can also build a new hermit crab tank using play sand which they love!

To help your crab through the molting process safely and comfortably, you may put a tank inside the main one. This way, the crab can quickly retreat and hide if it feels threatened or uncomfortable. Ensure to provide plenty of hiding places for the crab, so it has somewhere quiet and safe to go during this time. 

Isolating your crab in the main tank is the best option for crabs unprepared to deal with the molting process. This will give your crab the space it needs to molt and avoid potential stress. Using an isolating cage will help keep your crab safe and isolated while it molts.

Provide Privacy for Your Hermit Crab

Hermit crabs are creatures of the deep ocean who thrive in isolation. To provide them with the necessary privacy, place them in an area of the tank where they can’t see other crabs. 

Continuously monitor their behavior and adjust their environment as needed. Provide fresh water and food daily, and change the water twice a week if possible. When molting, hermit crabs need privacy and will retreat to a hiding spot to shed their exoskeleton.