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hermit crab smells like dead fish

Why Do Hermit Crabs Smell Bad?

Aquatic animals are popular with people who prefer low-maintenance pets. Unfortunately, anybody who has been to a fish market knows that marine life has a strong, distinct aroma.

So, do hermit crabs stink? Well, not if pet hermit crabs are healthy and their tank is cleaned regularly. Something is amiss if a hermit crab habitat is overwhelmingly bad.

The smell may not be from hermit crabs but something in the aquarium.

Why Would Hermit Crabs Smell Bad?

There are many reasons why hermit crabs smell, such as:


As per Crustaceana, hermit crabs release distinct pheromones when stressed.

Consequently, hermit crabs may seem smelly when you first bring them home. However, this will subside once they’ve had time to adjust to life in captivity.

Other common stress triggers of hermit crab stress include:

  • Insufficient substrate.
  • Lack of hiding places.
  • Overstimulation due to noise or light.
  • Excessive handling.
  • Unsanitary living environment.
  • Inappropriate temperature or humidity.
  • Loneliness because hermit crabs are a social species.

Also, you may notice that a hermit crab may lose a leg while under duress. This will grow back eventually during the next molt. However, the discarded limb will rot and release a foul smell.

do hermit crabs stink?


A tank’s temperature must be 80 degrees Fahrenheit and 80% humidity. Higher/lower temperatures and humidity cause hermit crabs to dry out and struggle with temperature regulation.

An overheated hermit crab will start to smell musty. Unless you correct this issue, the hermit crab will die. Check the temperature and use a misting spray to increase the humidity level.

Bathing water will help the hermit crab cool off, so provide a pool of salt and fresh water. Never use tap water because chlorine is toxic. Warm hermit crabs submerge in water to reduce their body temperature.

Buildup of Waste

Like all living things, hermit crabs must poop and pee. However, you’ll rarely see a hermit crab poop because they’re most active at night, and waste is stored in their shells.

Hermit crabs eliminate from the bottom of their abdomen, remaining in their shells while pooping and peeing. It’s too risky for hermit crabs to emerge unprotected. Also, hermit crabs may eat their own waste or flick 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 to prevent urine from mixing with water reserves inside the shell.

A single hermit crab’s poop or urine stream shouldn’t have any discernible smell. After a while, waste builds up and creates a lingering odor, especially if you keep many hermit crabs.

Spoiled Food and Spilled Water

Hermit crabs are natural scavengers with small bodies, so they rarely over-eat. If you leave excessive food in a hermit crab enclosure, it’ll spoil and start to smell.

Hermit crabs need fresh water and saltwater supplies for drinking and bathing, which can be spilled onto a sandy substrate. The smell of the beach is distinctive, but not everybody wants it in their home.

Do Hermit Crabs Smell When Molting?

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

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

  • Eat and drink more, building reserves of fat and water.
  • Start digging more frequently.
  • Develop a glazed look in its eyes.
  • Become lethargic.
  • Deliberately spill water to create humidity.
  • Turn an ashy, gray color.

Once a hermit crab is ready to molt, it’ll stay burrowed until the process is complete. This means you may need to tolerate an unpleasant scent for months.

Do Hermit Crabs Smell When They Die?

When a hermit crab dies, it releases an unmistakable smell.

Also, the behavior of surviving hermit crabs will reveal the death of a comrade. According to the Journal of Experimental Marine Biology and Ecology, this scent is more appealing than food.

If you keep many hermit crabs, other hermit crabs will become excitable. Also, they’ll start to gravitate toward a static, unmoving hermit crab.

The appeal of a dead body is the unique aroma it releases. When a hermit crab dies, it releases pheromones that other hermit crabs will detect.

This announces that a shell has or is set to become available. Then, the shell will be claimed.

What Do Dead Hermit Crabs Smell Like?

An expired hermit crab smells like dead fish. The problem is that the same can apply to a molting hermit crab, as the rotting smell comes from the discarded exoskeleton.

Before discarding an inanimate hermit crab, check if it’s alive.

Just because you found a rotten exoskeleton, the hermit crab may be alive in its shell, eating the exoskeleton when nobody is about to remain submerged during the molt.

Disposing of a Dead Hermit Crab

Sadly, captive hermit crabs do frequently pass away. If you’re certain the hermit crab is dead, dispose of the corpse ASAP because the smell will only grow more intense over time.

Don’t wait for other hermit crabs to consume their fallen comrade. They’ll likely do so, but this can take time. Eventually, the corpse will rot and smell bad.

Put the hermit crab in a small bag before putting it in the trash or burying it. If you choose the latter option, bury it relatively deep because the aroma of dead hermit crabs attracts stray and feral cats.

Also, thoroughly clean the tank to prevent the bad odor from lingering.

How To Keep Hermit Crabs from Smelling

If hermit crabs create an unsavory smell, you may be tempted to spray an air freshener, but you should never do so because you will inadvertently kill your hermit crabs.

Opening windows can disperse the aroma of hermit crabs, but it won’t address the problem. Remember, hermit crabs will emit an aroma for a reason.

Look into why your hermit crab is starting to smell and take these steps to address the issue:

Deep Clean

You should perform basic spot cleaning daily to remove waste or soiled substrate. Then, replace anything you’ve taken so the hermit crabs have at least 3 inches of substrate.

Clean the walls of an aquarium with a damp cloth. Hermit crabs like to climb, meaning they may have marked the walls with urine or feces. Avoid using any harsh chemicals, such as bleach.

Sometimes, you’ll need to perform a deep clean. Before beginning, put the hermit crabs in a temporary tank with substrate and hiding places.

Never deep clean while a hermit crab is molting.

Use a scoop to clear any soiled substrate. This will go some way to removing buried food. Every once in a while, completely replace all of the sand.

Clean the walls with a biodegradable, ideally homemade, solution. Vinegar that’s poured into filtered hot water works. Avoid tap water because traces of chlorine can cause illness or be fatal.

Wipe the walls and roof of the tank and allow it to dry before returning the hermit crabs.

do hermit crabs have an odor?

Changing Décor

Any toys or decorations within the tank may carry a scent, so they should be washed or replaced. There’s no harm in changing toys because hermit crabs like variety.

If you plan to reuse existing accessories, boil them in hot water for 3 minutes, as this will kill bacteria or fungi. This, in turn, should prevent any unpleasant smells from taking hold.

Plants and wooden logs shouldn’t be boiled, leading to rot and further deterioration. You can wash them by running a hot cloth over them. Then, allow everything to dry off.

New Shells

Hermit crabs enjoy having a wide array of shells in a habitat because this makes them feel safer. Also, it reduces conflict between hermit crabs. According to the Ecological Society of America, hermit crabs with small shells fight for larger shells for protection.

A hermit crab’s shell offers more than fortification, doubling up as a backpack. Hermit crabs may store food or water in a shell, which can grow stagnant, creating an unpleasant aroma.

Never physically remove a shell from the back of a hermit crab because it’ll be stressful. Instead, offer a selection of shells, as the hermit crab will change shells of its own accord.

When various shells are available, a hermit crab may change shells regularly. Once a shell is vacant, you can clean it. Boil the shell for a few minutes, dry it, and return it to the tank.


As natural omnivores, hermit crabs eat insects. Also, insects can act as natural cleaners of a hermit crab tank, reducing the likelihood of foul smells.

Common insects in a hermit crab habitat include booklice, springtails, and woodlice.

Perhaps more importantly, insects feast on dead moss, mold, and fungi, preventing unwanted scents from taking hold. While it’s not advisable to let insects overrun a tank, they have benefits.

Can Hermit Crabs Detect Bad Smells?

Hermit crabs have a good sense of smell because they have olfactory sensors on the antennae.

According to the Journal of The Royal Society Interface, hermit crabs detect odor through air currents. This aroma is trapped on the ground, where hermit crabs can process smell, which is how hermit crabs detect food.

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