hermit crab health issues

Is My Hermit Crab Healthy?

Last Updated on January 15, 2024 by Joanne Harper

Hermit crabs don’t experience the sort of illnesses that affect other pets, but that doesn’t mean they’re low-maintenance. You must provide appropriate care to keep hermit crabs in good order.

Is my hermit crab healthy? A hermit crab should retain a deep, vibrant skin color with bright, shining eyes. It should have a good appetite and enjoy digging, climbing, exploring, and interacting with its colony.

If a hermit crab grows passive and inactive, spending most of its time hiding, it’s likely unwell. Hermit crabs are easily stressed and can be vulnerable to toxicity.

How To Tell if Your Hermit Crab is Healthy

You can tell if a hermit crab is healthy by watching it. Happy and contented hermit crabs will be identified through their core characteristics and aesthetics:

Physical Appearance

Hermit crabs in peak physical condition will have 10 intact and functional limbs, including both claws.

A healthy hermit crab should also have both eyestalks, which will move periodically, and the eyes will be a bright and shiny black.

Don’t be alarmed if a hermit crab has missing a limb because these should grow back during the next molt, but consider why they would have shed a cheliped or leg.

What Color Should a Healthy Hermit Crab Be?

Color and skin tone are other ways to assess hermit crab health.

They should always maintain a bright and striking color unless it’s due to molt soon. In this instance, the color of the hermit crab should fade.

If this color remains consistent and striking, the hermit crab is healthy. If it starts fading to a dull gray and isn’t scheduled to molt, it’ll struggle with its health, likely due to a nutritional deficiency.

Activity Levels

Hermit crabs that have adjusted to captivity will be active and curious after dark. Hermit crabs are nocturnal animals, so they should come to live from dusk onward.

Hermit crabs love to dig, burrow, and climb. They’ll also frequently interact in their habitat, play fighting, antennae wrestling, and clambering over each other.

If one or more hermit crabs seldom move, showing little interest in movement or interaction with each other, their health is likely suffering.

Ensure this isn’t a consequence of stress or unacceptable living conditions.

healthy hermit crab

Behavior and Temperament

Hermit crabs enjoy the company of their kind and live in large colonies.

Within these groups, a social hierarchy will be formed. One hermit crab will likely become the alpha of the colony, and others will contentedly fall into line.

Hermit crabs will occasionally fight. They may quarrel over who’ll retain or earn their status as the leader of a group or appealing shells or other resources.

Even when hermit crabs experience a disagreement, they resolve their differences amicably.

Good Appetite

Hermit crabs should always have a hearty appetite and be ready to eat upon waking at dusk, especially if their meal is waiting for them. As soon as a hermit crab smells food, it’ll seek it out.

Sweet tastes and aromas will always appeal to hermit crabs, so stimulate their appetite with fresh fruit. Ensure saline water is found in a habitat.

According to BMC Neuroscience, salt water activates a hermit crab’s sense of smell.

If hermit crabs aren’t eating heartily, vary their diet sufficiently. As wild scavengers, hermit crabs are used to eating something different every day.

Shell Usage

Hermit crabs should be able to negotiate terrain with their shell on their back. The hermit crab should be able to hide within the shell without difficulty and not try to hang outside the shell.

If you find a hermit crab hanging outside its shell, it’s likely overheating and struggling with the conditions in the tank. Ensure the temperature doesn’t exceed 80°F.

Hermit crabs also need to choose a shell that isn’t too heavy. Something is amiss if a hermit crab selected a shell and is now too weak to support its weight.

Very occasionally, two hermit crabs will share a single oversized vessel.

Common Hermit Crab Health Issues

Hermit crabs are robust but can grow unwell if not cared for approximately. Typically, any health ailments will stem from these sources:

Stressed Out

Hermit crabs are wild animals that rarely breed under controlled conditions. Most pet hermit crabs start life in the wild, are captured before the sale, and are forced into captivity.

All hermit crabs will undergo post-purchase syndrome (PPS) when first introduced to a home. Hermit crabs that experience PPS will spend time hiding, usually under the substrate.

PPS can last days, weeks, or months. You must never force a hermit crab to interact against its will, especially when you have just bought it home.

Once a hermit crab overcomes PPS, it’ll start emerging from the substrate and spend more time in the open. This doesn’t mean it’ll never experience such upset again.

Three common stressors impact hermit crabs:

Boredom and Loneliness

Wild hermit crab colonies seldom number less than a hundred. Captive hermit crabs forced to live in solitude grow lonely, so always keep at least 4-5 together.

Boredom is also a concern for hermit crabs. Ensure they have plenty to do, including toys, climbing frames, and hiding places. Hermit crabs spend their lives in one location, so make it an interesting home.

Poor Living Conditions

Hermit crabs need certain living conditions to thrive, as they hail from tropical and subtropical climates.

Tank size is important, so never place hermit crabs in an aquarium smaller than 10 gallons. Also, consider the temperature and humidity.

As ectotherms, hermit crabs grow inactive and eventually risk death if they’re too cold. Keep the temperature of a hermit crab enclosure at around 80°F.

Humidity is equally vital to keeping hermit crabs safe. They breathe through their gills, which must be kept moist, so a humidity level of around 80% is essential.

Get a hygrometer to monitor humidity, misting a habitat if necessary.

Excessive Handling

Hermit crabs can learn to tolerate being handled but never actively enjoy it.

Don’t adopt hermit crabs expecting the company of cuddly, playful pets. The more you force hermit crabs into physical interaction, the more stressed they’ll become.

Is My Hermit Crab Healthy?


Some everyday items can sicken and kill hermit crabs, including:

  • Paint. Never purchase a shell that has been decorated ahead of selling or paint shells that your hermit crabs may wear.
  • Tap water. Water from a tap contains chlorine and heavy metals that kill hermit crabs. Use purified water or, better yet, bottled water.
  • Cleaning materials. All hermit crab enclosures must be deep cleaned every 1-3 months, but avoid using bleach and toxic chemicals.
  • Scented candles and essential oils. These can contain airborne irritants that cause distress, sickness, and death in hermit crabs.

Aerosol sprays, especially fly sprays, mustn’t be used around a hermit crab enclosure.

Wrong Diet

According to The Biological Bulletin, hermit crabs avoid foods that cause an adverse reaction, which means they innately understand their dietary needs.

If a hermit crab lacks calcium or protein, its health will suffer. A mineral deficiency leads to weakness in the exoskeleton, potentially causing shell rot and bacterial infection.

Ensure the hermit crabs are eating heartily, varying their diet daily. If you notice holes in a hermit crab’s exoskeleton, increase its calcium and protein.


According to the Journal of Experimental Marine Biology and Ecology, up to 150 parasites impact hermit crabs. Mites can make a hermit crab weak and uncomfortable.

A hermit crab with mites will seek a way to relieve the constant itching. If bathing doesn’t work, a hermit crab may shed its limbs or sever its eye stalks to remove the irritation.

Mite infestations can be hard to spot before they take hold. To minimize the risk of an enclosure becoming infested, regularly clean it and allow the hermit crab to bathe in saline water.