Home » Why Do Hermit Crabs Make Bubbles? (Brown Bubbling)
why is my hermit crab bubbling?

Why Do Hermit Crabs Make Bubbles? (Brown Bubbling)

Hermit crabs have some confusing behaviors. Although uncommon, it’s concerning to see your hermit crabs foaming at the mouth. Unfortunately, brown bubbles in hermit crabs are rarely normal or healthy.

Hermit crabs produce brown bubbles due to injury, illness, dehydration, overheating, or post-purchase syndrome. Other explanations include dirt in the shell and loneliness. If your hermit crab has a single grey or black bubble that seems to be stuck to its abdomen, it’s about to commence its molting phase.

If your hermit crab is bubbling, you must remove any stressors. This may involve separating the hermit crab from aggressive members of the tank or improving water sources. A heater may need to be adjusted, changed in position, or removed entirely. Once the alterations have been made, all you can do is wait for the brown bubbling to stop.

Is It Bad for Hermit Crabs To Blow Bubbles?

A hermit crab blowing bubbles will appear to have frothed at the mouth. It may also be covered in little, soapy-looking bubbles on certain areas of its body. Some species of crabs can do this as a way to improve their breathing on land. In hermit crabs, it’s usually a bad sign. The severity will depend on the hermit crab itself and its living conditions.

For example, the hermit crab may bubble when there’s dirt in its shell, which is a way to clean itself. You can assist your hermit crab by providing more water so that it can flush out its shell properly.

However, the hermit crab may also bubble if it’s injured or dehydrated. These cases may be life-threatening. If you notice bubbling, be ready to take swift action. If the hermit crab also emits a foul or fishy smell, this is a sign of danger.

Why Your Hermit Crab Is Bubbling

Bubbles are usually a sign of distress in hermit crabs. This stress can be caused by:


To thrive, hermit crabs must be kept in a warm environment. However, if temperatures are overly high, they’re prone to overheating and dehydration.

Overheated and dehydrated hermit crabs will create bubbles to aerate their gills. Bubbling is often a last-ditch effort, so it may already be too late. Thankfully, you can notice overheating before it causes irreversible damage.

An early symptom is excessive digging. If your hermit crab is digging more than usual, it’s probably trying to find better conditions. According to Ecology, even wild hermit crabs dig deeper to find cooler, moister, and safer places. If you notice this behavior in most of your hermit crabs, check the tank for problems.

Usually, a misplaced heater is the culprit. If your tank has a heater, be sure it’s located on the side of the tank, not the bottom. Placing it at the bottom heats the substrate, which can be a fire hazard. It should be used to heat the air.


Injuries are commonly due to attacks from other hermit crabs within the tank. If your hermit crab is new, the injury may have occurred during its stay in the pet store or its journey to your home.

An injury could cause your hermit crab to bubble at the mouth. Just as humans will breathe harder when in pain, your hermit crab may aerate its gills when distressed. Commonly, bubbles from injured hermit crabs are brown. If you notice this symptom, there is a chance your hermit crab is dying.

However, if your hermit crab is not emitting a foul smell, it may still have a chance of recovering. Your first response should be to separate the injured hermit crab from other members of the tank without moving the injured hermit crab. To do this, you can create a barrier around it. Alternatively, you can transfer all your other hermit crabs to a different tank for the time being.

After that, ensure that your hermie has access to water and food. It will need to recover in peace, which takes time.


A less concerning reason for bubbling hermit crabs is dirt. If your hermit crab’s shell is dirty, it may irritate its exoskeleton, as well as its abdomen. Bubbling is a way for your hermit crab to lessen the irritation, as well as clear out the dirt or debris stuck inside.

If your hermit crab is bubbling due to irritation, the bubbles will often be clear. They will also be found in the area between its body and the shell.

If you think that your hermit crab is bubbling because of dirt and irritation, be sure to check your water sources. Hermit crabs do not need to be given baths. Instead, they will bathe themselves.

They will normally take a dip in water to clear out the debris stuck in their shell. If your hermit crab’s shell is dirty, that means it doesn’t have the right space to clean itself.

hermit crab blowing bubbles

Post-Purchase Syndrome

Newly-purchased hermit crabs, especially those bought from pet stores, can get post-purchase syndrome. Post-purchase syndrome refers to the illnesses and diseases that hermit crabs get immediately after purchase.

These are usually caused by the hermit crabs’ previous living conditions. Unfortunately, hermit crabs are often kept in subpar enclosures at pet stores. Even if the store properly cared for its hermies, the hermit crab may have had to travel hundreds of miles before it arrived. Many things could happen to a hermit crab during this time. Symptoms of post-purchase syndrome include:

  • Leg loss
  • Lethargy
  • Weakness
  • Loss of appetite

Of course, post-purchase syndrome has a lot of stressors. If your hermit crab is newly bought and producing bubbles, it could be a sign of stress. At this stage, the damage may have already been done.

Post-purchase syndrome ends with molting. During stressful situations, crabs will put off molting, even though it’s detrimental to their health. A hermit crab will begin molting once it believes that it’s in a safe environment to do so. After a successful molt, you can be certain that post-purchase syndrome has been resolved.


On that note, your hermit crab may appear to bubble due to its molting period. If your hermit crab is molting, it often develops a small, grayish-black bubble on the left side of its abdomen. This bubble isn’t actually a bubble. Instead, it is a reserve of fat and water that the hermit crab can access during the molting process.

Molting takes a lot of energy and can be stressful for hermit crabs. During the process, your hermit crab will need water and nutrients. However, a hermit crab is unable to move while its new exoskeleton hardens. For this reason, it will need to have a reserve of water and food that it can access. Other symptoms of molting include:

  • Excessive digging
  • Eating and drinking more than usual
  • Weakness and lethargy
  • Restlessness
  • Grey or ashy body, tips of legs, claws, and eye stalks turn white
  • Gel limb, or regenerating limbs


As a rule of thumb, a bubbling hermit crab is stressed. Many different factors may cause stress. However, stress by itself can also be enough to make your hermit crab bubble.

Aside from the problems listed above, your hermit crab may be stressed if it’s alone in its tank. Despite their name, hermit crabs live in groups. When kept solo, a hermie will grow lonely and upset, which can lead to bubbling. By placing them in the company of other hermit crabs, this behavior should pass.

What To Do If Your Crab Is Bubbling

If your hermit crab is making bubbles due to a life-threatening issue, there’s no direct treatment you can offer.

However, you can lessen the factors causing your hermit crab to bubble. If your hermie isn’t beyond help, this can facilitate its recovery. If the reason for the bubbling is mild, like stress, that can also remove the problem and keep it from escalating into a worse state.

Do Not Handle

If your hermit crab is making bubbles, you shouldn’t attempt to move it. If it’s bubbling due to an injury, handling it could harm your pet hermit crab further.

If it’s bubbling due to stress, the invasion of its space by a human hand or object could stress it out even more. Instead, be sure to leave your crab secure exactly where it is, and make modifications around it.

Check Tank Conditions

You can best assist your hermit crab by double-checking its tank conditions. Hermit crabs are surprisingly independent creatures. If left alone in good conditions, they will stand their best chance of making a full recovery.

Humidity Levels

Ensure that your tank has enough humidity. A humid environment is important for hermit crabs to thrive. According to The Proceedings of the Royal Society, hermit crabs use humidity to find their food. The ideal humidity depends on the type of hermit crabs that you own. If you’re unsure, a good rule of thumb is 70-80% humidity levels.

If your humidity is less, mist the tank with non-chlorinated water or bottled water. Seek out the most effective ways to raise humidity levels permanently, like adding damped moss to your tank.

hermit crab blowing bubbles

Temperature Levels

After checking humidity, ensure your tank has the right temperatures. They should not exceed 85 degrees Fahrenheit. Doing so can dehydrate hermit crabs, which is a common cause of bubbles. During the day, temperatures should be 75 to 85 degrees Fahrenheit. At night, 65 to 75 degrees Fahrenheit is normal.

Should your aquarium need more heat, you can add a heater or use insulators. For example:

  • Aluminum foil with the shiny side facing inside the tank.
  • Cover with foam board or Styrofoam.
  • Opt for an aquarium cover to create a more permanent fixture.

Water Sources

Hermit crabs need a shallow dish of freshwater and saltwater. Water should be dechlorinated, as chlorine is harmful to hermit crabs.

Your hermit crabs must have an easy way to get in and out of their pool. Otherwise, your hermit crab can be in danger of drowning. Pebbles, rocks, or netting can be used as a stair step or ladder.

If you look over your tank and find no problems, check the accuracy of your thermometers and hygrometers.

How Long Until My Crab Stops Blowing Bubbles?

If your hermit crab continues to bubble, all you can do is wait and hope for signs of progress.

If the reason for bubbling is too severe, then you will notice the bubbles growing brown and developing a fishy smell. You should make your hermie feel comfortable and wait for it to pass away.

However, the hermit crab may continue blowing clear bubbles as it heals or calms down. After the stressors are removed, the hermit crab will recover and stop this sign of distress.

The amount of time this takes depends on how quickly the stressors are removed from your hermit crab’s tank. For example, it may take more than 1-2 days for the tank conditions to adjust to revised humidity levels.