why is my hermit crab bubbling?

Why Do Hermit Crabs Make Bubbles? (Brown Bubbling)

Last Updated on: 20th October 2023, 02:22 pm

Hermit crabs produce brown bubbles due to injury, illness, dehydration, overheating, post-purchase syndrome, dirt in the shell, and social isolation.

If a hermit crab has a single grey or black bubble that seems to be stuck to its abdomen, this could mean it’s about to commence the molting phase.

When a hermit crab is bubbling, remove the stressors. For example, separating the hermit crab from hostile tank members or adjusting the temperature and humidity levels can be beneficial.

Is It Bad for Hermit Crabs To Blow Bubbles?

A hermit crab blowing bubbles will appear frothed at the mouth. Also, it may have tiny soap-like bubbles on specific body parts.

Some species of crabs can do this to improve their breathing on land. In hermit crabs, it’s usually a negative sign, but the severity depends on the hermit crab and its living conditions.

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

A hermit crab may bubble when injured or dehydrated, which can be life-threatening. This can be a warning sign if the hermit crab also emits a foul or fishy smell.

Why Is My Hermit Crab Bubbling?

Bubbles are usually a sign of distress in hermit crabs due to:


To thrive, hermit crabs must be kept in a warm environment. However, if the temperature is too hot, hermit crabs are prone to overheating and dehydration.

Overheated and dehydrated hermit crabs create bubbles to aerate their gills. Bubbling is often a last-ditch attempt to save itself, but you can observe overheating before it causes irreversible damage.

If a hermit crab is digging more than usual, it’s trying to find more suitable conditions.

According to Ecology, wild hermit crabs dig deeper to find cool, moist, and safe places. Check the tank’s temperature and humidity levels if you observe this behavior.

If the tank has a heater, put it on the side of the tank, not the bottom. Placing it at the bottom of the tank heats the substrate, which can be a fire hazard. A heater should be used to warm up the air.


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

An injury could cause a hermit crab to bubble at the mouth. Just as humans breathe harder when experiencing pain, a hermit crab may aerate its gills when distressed.

Commonly, bubbles from injured hermit crabs are brown. If you notice this symptom, there’s a chance the hermit crab is dying.

If a hermit crab isn’t emitting a foul smell, it may be able to recover. Separate the hermit crab from other tank members without moving the injured one.

To do this, create a barrier around the injured hermit crab. Alternatively, temporarily transfer the other hermit crabs to a different tank.


If a hermit crab’s shell is dirty, it may irritate its exoskeleton and abdomen. Bubbling is a way for a hermit crab to lessen the irritation and clear out dirt or debris.

The bubbles will often be transparent if a hermit crab is bubbling due to irritation. They’ll also be found between the body and the shell.

Check the water sources if you think a hermit crab is bubbling due to dirt and irritation.

They’ll usually enter the water to clear out debris stuck in their shell. If a hermit crab’s shell is dirty, it doesn’t have enough space to clean itself.

hermit crab blowing bubbles

Post-Purchase Syndrome

Newly-purchased hermit crabs, especially those bought from seafront stores with painted shells, can get post-purchase syndrome (PPS).

PPS refers to hermit crabs having difficulty coping with environmental change and traveling hundreds of miles to their new home after being taken from the beach.

The symptoms of post-purchase syndrome include:

If a hermit crab is newly bought and produces bubbles, it’s likely due to stress.

Post-purchase syndrome ends with molting. Although it harms their health, hermit crabs will delay molting during stressful situations.

A hermit crab will begin molting once it’s in a safe environment.


If a hermit crab is molting, it often develops a small, grayish-black bubble on the left side of its abdomen. This isn’t a bubble but a reserve of fat and water the hermit crab can access during molting.

Molting takes a lot of energy and can be stressful for hermit crabs. During the process, a hermit crab will need water and nutrients.

A hermit crab can’t move while its new exoskeleton hardens. For this reason, it’ll need a reserve of water and food it can access.

Other signs of molting in hermit crabs 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.


Aside from the problems discussed, a hermit crab may be stressed if left alone in its tank.

Despite their name, hermit crabs live in colonies of up to 100. Without companionship, a hermit crab will grow lonely and distressed, leading to bubbling.

By introducing other hermit crabs, the stress should dissipate.

What To Do If A Hermit Crab Is Bubbling

There’s no treatment if a hermit crab produces bubbles due to a life-threatening condition. However, you can minimize the factors causing a hermit crab to bubble.

If a hermit crab isn’t beyond help, this can facilitate its recovery. If the reason for the bubbling can be resolved, like stress, you can remove the stressor and await gradual recovery.

Avoid Handling

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

If bubbling due to stress, the invasion of its space by a human hand or object will exacerbate matters.

Check Tank Conditions

You can best assist a hermit crab by checking the tank conditions. If left alone in suitable conditions, they’ll have a better chance of recovering fully.

Humidity Levels

A humid environment is essential for the survival of hermit crabs because it’s needed to breathe.

According to The Proceedings of the Royal Society, hermit crabs use humidity to find food. The ideal humidity level depends on the hermit crab species, but 80% is usually optimal.

If the humidity is less, mist the tank with non-chlorinated or bottled water. Also, changing the substrate or adding moss to the tank can increase the humidity level.

hermit crab blowing bubbles

Temperature Levels

After checking humidity, ensure the tank’s temperature is 80 degrees Fahrenheit. Doing so can dehydrate hermit crabs, and this is a common cause of bubbles.

Should the aquarium need more heat, add a heater or use insulators. Examples include:

  • Aluminum foil with the shiny side facing inside the tank.
  • Cover with foam board or Styrofoam.

These adjustments should ensure that the tank is sufficiently warm.

Water Sources

Hermit crabs need a shallow dish of fresh water and salt water.

Water should be dechlorinated (not tap water), as chlorine harms hermit crabs.

Hermit crabs require an easy way to get in and out of their pool. Otherwise, it’s in danger of drowning. Pebbles, rocks, or netting can be used as a stair step or ladder.

How Long Until My Hermit Crab Stops Blowing Bubbles?

If a hermit crab continues to bubble, all you can do is await signs of progress.

A hermit crab may continue blowing clear bubbles as it heals or calms down. Once the stressors are removed, the hermit crab will recover and no longer show this sign of distress.

The time this takes depends on how quickly the stressors are removed from the tank.

If the reason for bubbling is too severe, you’ll notice the bubbles growing brown and developing a fishy smell. If so, make the hermit crab feel comfortable and wait for it to pass.