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Why Do Hermit Crabs Smell Bad?

When contemplating getting a new pet, the smell that they emit is often a key consideration. Aquatic animals are a popular choice among people that prefer low-maintenance, non-smelly companions. Like any living creature, though, hermit crabs can generate foul odors.

A stressed hermit crab will release smelly pheromones. Hermit crabs can also dry out through overheating and a lack of humidity. Waste, uneaten food, and water spilled on the substrate can also create odors. Most notable of all is the rotten fish smell associated with dead tissue. This could mean the hermit crab has died or is molting.

When it comes to scent and hermit crabs, no news is good news. If you cannot detect any smell, it suggests that these crustaceans are happy and healthy. Offensive odors always merit investigation. What’s more, the cleaning process must be safe for hermit crabs.

Do Hermit Crabs Have an Odor?

Anybody that has visited a fish market knows that marine life has a distinct aroma. So, do hermit crabs stink? Well, not if your pets are healthy and calm. If your hermit crab habitat is offensive to the nose, something is clearly amiss.

The smell may not be coming from hermit crabs. It could be something within the aquarium. Cleaning a hermit crab’s home is important. Forget anything that you’ve heard about hermit crabs being easy to care for pets as you cannot be complacent about hygiene.

If you notice a smell and your hermit crab is not hiding, pick it up. Give the hermit crab a sniff. This will help you understand if the scent is specifically coming from your hermit crab. If not, you’ll need to step up the cleaning regime.

Why Would Hermit Crabs Smell Bad?

There are many reasons why a hermit crab would start to smell, and none of these are natural occurrences. Determine why the smell is coming from your hermit crabs and take action. Here’s why it happens:


As per Crustaceana, release distinct stress pheromones when stressed. This means that hermit crabs may seem smelly when you first bring them home. However, hermit crabs need time to adjust to life in captivity. You will also likely find that a new hermit crab burrows and hides.

Hermit crabs are easily stressed, so you’ll need to watch this. Other common triggers of hermit crab stress include:

  • Insufficient substrate
  • A lack of hiding places
  • Overstimulation through noise or light
  • Excessive handling
  • Unsanitary living environments
  • Inappropriate temperature or humidity
  • Loneliness, as hermit crabs are a social species

You may also notice that a stressed hermit crab sheds body parts. A hermit crab may lose a leg while under duress. This will grow back eventually. The discarded limb will rot and release a foul smell, though.

do hermit crabs stink?


Hermit crabs require a particular temperature and humidity level in an enclosure. An aquarium must always be set to around 80 degrees Fahrenheit and 80% humidity. Higher temperatures or lower humidity make a hermit crab dry out.

An overheated hermit crab will start to smell musty. This is an emergency. Without rectifying this issue, the hermit crab will die. Check the temperature and use a misting spray to enhance humidity.

Bathing water will also help the hermit crab cool off. Provide two pools of water. One should be saltwater and the other fresh. Just avoid tap water as chlorine is toxic. Warm hermit crabs submerge in water to reduce body temperature.

Buildup of Waste

Like all living things, hermit crabs need to eliminate. You will rarely see a hermit crab poop. This does not mean the hermit crab is constipated. It just means the waste is being stored in a shell.

Hermit crabs eliminate from the bottom of their abdomen. They remain in their shell while pooping. It’s too risky to emerge to use the bathroom unprotected. The hermit crab may eat its own waste. Alternatively, it may clean its shell by flicking excrement onto the substrate.

The opposite applies to urination as hermit crabs pee through a tract on their head. The urinary tract is located in the antennal glands. Hermit crabs poke their head out of the shell and pee straight into the substrate. This prevents urine from mixing with water reserves in the shell.

A single hermit crab poop or urine stream should not have any discernible smell. After a while, though, waste will build up. Equally, hermit crabs do not like being surrounded by their own waste. Regular spot cleaning of shells and substrate is advisable.

Spoiled Food and Spilled Water

Hermit crabs are natural scavengers with small bodies. This means they rarely over-eat. If you leave excessive food in a hermit crab enclosure, it will be left to spoil. Naturally, this can start to smell.

The same applies to spilled water. Hermit crabs need fresh and saltwater supplies for drinking and bathing. This can be spilled onto a sandy substrate. The smell of the beach is distinctive and often pleasurable. Not everybody wants it in their home, though.

Consider how much water your hermit crab is storing in its shell. Hermit crabs retain water in case of a shortage. They also use this to drink and bathe while molting. This water can grow stagnant, though. It may need emptying next time the hermit crab changes shells.

Do Hermit Crabs Smell When Molting?

Molting is one of the main occasions that a hermit crab will smell. This is unavoidable, as hermit crabs need to molt in order to survive.

Molting is the process of a hermit crab shedding its skin. The existing exoskeleton will drop off and a new, larger one will grow. This discarded exoskeleton is dead tissue. It will start to rot and smell as a result.

Many owners mistake the molting process for death in hermit crabs, mainly due to this stench. Ensure you learn the difference. Ahead of molting, a hermit crab will:

  • Eat and drink more, building reserves of fat and water
  • Start digging more and more frequently
  • Develop a glazed look in the eye
  • Become lethargic and lazy
  • Deliberately spill water on the substrate to create moisture
  • Turn to an ashy, gray color

Once it’s ready to molt, the hermit crab will burrow until the process is complete. This means you may need to tolerate an unpleasant scent for weeks, or even months. Do not rush to write off your hermit crab as dead. Try your best to be patient and tolerant.

Do Hermit Crabs Smell When They Die?

When a hermit crab dies, it releases an unmistakable smell. The behavior of surviving hermit crabs will also reveal the death of a comrade. As per the Journal of Experimental Marine Biology and Ecology, this scent is more appealing than food.

If you notice a strong smell from an aquarium, look closer. If you keep multiple hermit crabs, others may be excitable. They will also start to gravitate toward a static, unmoving crustacean. This is not due to morbid curiosity.

It is true that hermit crabs will eat a dead friend. As natural scavengers, hermit crabs will eat anything to survive. It’s inadvisable to allow this, though. The hermit crab died for a reason. This could have been an ingested toxin.

The appeal of a dead body is the unique aroma that it releases. When a hermit crab is dying, it releases pheromones detected by other crustaceans. This is not a cry for help. Rather, it is announcing that a shell is set to become available. This shell will then be claimed.

What Do Dead Hermit Crabs Smell Like?

An expired hermit crab smells like dead fish. This putrid stench is unmistakable and impossible to ignore. The trouble is that the same can also apply to a molting hermit crab. The rotting smell comes from a discarded exoskeleton.

Before mutilating and discarding an inanimate hermit crab, check whether it could be alive. Just because you found a rotten exoskeleton, the hermit crab may be alive in its shell. It is eating the exoskeleton to remain submerged during the molt.

This can obviously lead to issues. Nobody wants to live with the smell of rotten fish in the home. Alas, discarding the exoskeleton could lead to malnourishment for a molting crab. Tolerate the scent as long as you can unless you are certain the crustacean is dead.

Disposing of a Dead Hermit Crab

Sadly, captive hermit crabs do frequently pass away. If you are certain that the hermit crab is dead, dispose of the corpse ASAP. The smell will only grow more pungent over time.

Do not wait for other hermit crabs to consume their fallen comrade. They will do so, but this can take time. Eventually, the corpse will rot. This could make additional hermit crabs sick.

Dispose of the dead hermit crab, wearing gloves. Wrap it in a sturdy bag. This will go some way to masking the smell. You can then leave this in the trash or bury it. If you choose the latter option, bury it deep. The aroma of dead hermit crab may attract feral cats.

It is also advisable to conduct a thorough clean of the habitat. The scent will linger. Eventually, this will stop exciting other crustaceans in the habitat. Instead, it will cause stress.

How to Keep Hermit Crabs from Smelling

If hermit crabs are creating an unsavory smell, you may be tempted to spray air freshener. Don’t do it because you will inadvertently kill your hermit crabs. This will create an even worse odor. You must learn how to make hermit crabs not smell more safely.

Any form of aerosol creates particles that make their way into a hermit crab aquarium. These can land in food and water, poisoning a hermit crab. Even if this not the case, sprayed chemicals can pollute the small lungs of a crustacean.

Opening windows may help disperse the aroma of a hermit crab. If the temperature of the aquarium remains at 80 degrees, this is safe. You may need to invest in a heat lamp to retain this appropriate temperature.

Remember, hermit crabs will create aromas for a reason. Prevention is better than cure. Look into why your hermit crab is starting to smell and react accordingly. Better yet, take measures to stop the scent from arising in the first place.

Cleaning of Habitat

Regular cleaning of a hermit crab habitat is essential. Each day, you should perform basic spot cleaning. This will remove any waste or soiled substrate. Take a spoon to the top layer of the sand. Replace this so that the crustacean always has at least three inches of substrate.

You should also clean the walls of an aquarium. Just use a damp cloth. Hermit crabs like to climb, so they may have marked walls with urine or feces. Avoid using any harsh chemicals here. Bleach is dangerous, but water is fine.

From time to time, you will need to perform a deeper clean. Before you start this, regime your hermit crab in a temporary abode. Some kind of playpen, complete with substrate and hiding places, is ideal. Never attempt a deep clean while a hermit crab is molting.

Start with the substrate. Use a scoop to clear substrate, akin to changing a feline litter tray. This will go some way to removing buried food. Every once in a while, completely replace all sand. Always stick with a familiar substrate that hermit crabs know and enjoy.

do hermit crabs have an odor?

Clean walls with a biodegradable, ideally homemade, solution. Vinegar poured into filtered hot water will work. Avoid tap water, as the hermit crab may lick the walls of its habitat. Traces of chlorine will be fatal.

Wipe the walls and roof of the aquarium. Allow it to dry completely before returning your hermit crab. You could also take this opportunity to rearrange the layout of the aquarium. This gives the hermit crabs new territory to explore.

Changing Décor

It is not just the substrate of a hermit crab’s enclosure that will start to smell. Any toys or decorations within the tank may also carry a scent. These should be washed or replaced whenever you complete a deep clean.

There is no harm in changing toys completely. Hermit crabs enjoy plenty of variety. You can always locate new decorations. Do not purchase fish tank accessories from a pet store. These contain paints and dyes that run in humid conditions. Stick with natural rocks and logs.

If you plan to re-use existing accessories, boil them in water. Around three minutes will be long enough. This will kill any bacteria or fungi growing on the decoration. This, in turn, should prevent any unwelcome smells from taking hold.

Plants and wooden logs should not be boiled. This will lead to rot and further deterioration. You can wash them with hot water, though. Run a hot cloth over these decorations. Let them dry before returning them to an aquarium. Better yet, replace them entirely.

Replacing Shells

Hermit crabs enjoy having a wide array of shells in a habitat. This makes the crustacean feel safer. It also reduces conflict between hermit crabs. As per the Ecological Society of America, hermit crabs with small shells fight for larger protection.

A hermit crab shell offers more than just fortification, though. It doubles up as a crustacean backpack. Hermit crabs may store food or, more commonly, water in a shell. This can grow stagnant, leading to an unpleasant aroma.

Never physically remove a shell from the back of a hermit crab. This will cause a great deal of stress. You will also likely be pinched for your trouble. Instead, offer a selection of shells. The hermit crab will choose to change shells of its own accord.

When a variety of shells are available, a hermit crab may change multiple times a week. While a shell is vacant, you can clean it up. Treat this the way may you would a decoration. Boil the shell for a few minutes, dry it and return it.

It is good to retain existing shells as long as they are clean. You can be assured that these shells will not harm a hermit crab. There is nothing wrong with adding more choices, though. The greater shell selection a hermit crab has, the more it will change.

Cleaning Insects

As natural omnivores, hermit crabs eat insects. Bringing bugs into a hermit crab enclosure offers more than just a snack, though. Insects can act as natural cleaners of a hermit crab aquarium. This will help with foul smells.

Common insects you’ll find in a hermit crab habitat include booklice, springtails, and woodlice. These bugs will be drawn to wooden decorations in the aquarium. They will not hurt the hermit crab and are edible.

Perhaps more importantly, these insects feast on dead moss, mold, and fungi. This will prevent unsavory scents from taking hold. While it is not advisable to let insects overrun an aquarium, they do have uses.

Can Hermit Crabs Detect Bad Smells?

Hermit crabs have a surprisingly good sense of smell, considering they have no conventional nose. This is because hermit crabs have hundreds of olfactory sensors located on the antennae.

As per the Journal of The Royal Society Interface, hermit crabs detect odor through air currents. The antennae are flicked, detecting airflow. This aroma is trapped on the ground, where the hermit crab can process the smell. This is how hermit crabs detect food.

Hermit crabs also use this technique to determine between predators and prey, as per Animal Behavior. Hermit crabs grow distressed by foul smells, though. They do not like odors any more than owners.

A happy, healthy hermit crab in a sanitary environment should smell comparatively neutral. Like all animals, hermit crabs can generate odors. If hermit crab smells fishy, you need to investigate why.