Halloween Moon Crab: A Complete Guide & Pictures

Colorful Halloween moon crab on sandy bottom

The Halloween moon crab is not your average crab. These crabs come from the warm areas of Central and South America and are known for their Halloween-like colors. But what else is special about them?

This guide has everything you need to learn about these eye-catching crabs. We’ll talk about where they come from, how they behave, and what you must do to take good care of a Halloween moon crab.

Whether you’re considering getting a moon crab or simply curious, this guide covers everything. Read along and learn about their diet, habitat needs, and how to keep them happy and healthy.

Halloween Moon Crab Quick Facts

Common Name:Halloween Moon Crab
Other Names:Moon Crab, Purple Moon Crab, Harlequin Crab, Harlequin Land Crab, White Spot Crab
Scientific Name:Gecarcinus quadratus
Tank Size (Minimum):15 gallons (~60 liters)
Difficulty of Keeping:Medium
Breeding Difficulty:Very Difficult
Size:Up to 2–2.5 inches (5–6 cm)
Optimal Temperature:24°C–30°C (~75°F–85°F)
Water Type:Freshwater and shallow saltwater bowls (dechlorinated/purified water recommended)
Moisture Requirement:At least 80%
Substrate Depth:More than 6 inches (15 cm)
Diet:Mostly herbivore/omnivore
Lifespan:Up to 8 years
Color Form:Purple, black, and orange
Lighting Needs:Low or red light, mimicking nocturnal conditions
Social Structure:Solitary/territorial; not suitable for cohabitation with other crabs
Activity Level:Nocturnal, active at night; skilled climbers

What Is a Halloween Moon Crab?

Halloween moon crab carrying sand

The Halloween moon crab is a crab species known for its purple, black, and orange colors. These small terrestrial crabs come from tropical areas and are popular for their Halloween-themed colors and unique behavior. They are also known as purple moon crabs, harlequin crabs, and white spot crabs.

The striking colors of Halloween moon crabs result from natural adaptations and survival strategies. These bright colors help them blend into their tropical habitat, attract mates, and fend off predators. 

In the wild, Halloween moon crabs are typically found in coastal forests, often located far from bodies of water. 

Meanwhile, in homes, moon crabs are usually enclosed in specialized terrariums that replicate their natural environment. These terrariums must balance land and water elements to simulate the crabs’ unique lifestyle.

While Halloween moon crabs are increasingly popular in the pet world, caring for them is not that simple. Aspiring crab keepers need to thoroughly educate themselves before bringing a moon crab home.

Why Is It Called a Halloween Moon Crab?

The Halloween moon crab owes its catchy name to its color combination. These crabs boast a striking combination of purple, black, and orange — colors that strongly resemble the hues of Halloween.

The term “Halloween moon crab” likely emerged within the pet trade community, although no definitive record points to its exact origin or who coined the name.

Other names, such as “purple moon crab” and “harlequin land crab,” seem to have originated in the same way. All in all, these names serve as vivid descriptions meant to capture the crab’s standout traits.

Meanwhile, the scientific name for the Halloween moon crab, Gecarcinus quadratus, likely comes from established scientific naming conventions.

Gecarcinus‘ comes from Greek words meaning ‘land crab,’ and ‘quadratus‘ is a Latin word that means ‘square-shaped,’ which might refer to the angular appearance of the crab. 

Halloween Moon Crab Origin and Natural Habitat

Halloween moon crab nestled under wood

While there are only a handful of key details about the origin of the Halloween moon crab, its natural habitat is diverse and interesting.


The Halloween moon crab, known as Gecarcinus quadratus, was first identified in 1853 by Henri Louis Frédéric de Saussure.

Known for his significant contributions to entomology and taxonomy, de Saussure had a wide range of interests within the study of insects.

His passion for entomology developed during his time at the University of Geneva. De Saussure’s extensive travels led to the documentation and discovery of various species, including the Halloween moon crab.

Natural Habitats

The Halloween moon crab is found in coastal areas of Central and South America, from Mexico to Panama. It thrives in warm, humid environments like mangroves, dunes, and rainforests.

These crabs are nocturnal and are known for digging burrows, which can be as long as 5 feet. They spend much of their adult life in coastal forests above the high tide line, where conditions are safe and humid.

Though they live on land, they return to the ocean to breed. Their diet is primarily plant-based, including leaf litter and seedlings.

I first encountered Halloween moon crabs in their natural habitat on a trip to Costa Rica. It was dusk, and these crabs, with their vivid legs and purple claws, were moving swiftly around the mangrove roots.

I watched them scurry around, picking up leaves and bits of food right next to their burrows. These burrows were situated near where the forest meets the open land.

Halloween Moon Crab Physical Characteristics

Halloween moon crab on a sandy beach

The Halloween moon crab is a small and colorful crustacean. It has a compact body with a hard, rounded shell or carapace, measuring about 2 to 2.5 inches across. This dark shell is likened to the deep midnight sky. 

Connected to its shell are eight slender legs and two prominent claws, extending the crab’s span to around 4 inches in total.

The legs of Halloween moon crabs are fiery orange-red, while their claws are deep purple with blue tones that fade into softer white at the tips. 

On the back of their dark shells are two small white spots. These spots stand out against a dark background. There are also orange spots near their eyes. 

All these unique marks make the Halloween moon crab different from other crab species, giving it its signature look. But did you know that these crabs change in appearance every once in a while?

This process is called molting, and it occurs every 18 months. During molting, the moon crab’s vibrant shell becomes dull as it sheds its outer layer to grow a new one. 

As the crab molts, the shell may seem loose, a sign that it is withdrawing from its old exoskeleton. Once shed, the new shell will appear soft and pale, but it gradually hardens and regains its color as time goes on. 

Watch this video to see a Halloween moon crab in action:

What Is A Halloween Moon Crab?

To tell between a male and female Halloween moon crab, check the abdomen shape: males have a narrow plate while females have a broader one. 

Additionally, males typically have larger, brighter claws and more saturated colors than females.

Fun Fact: There is a group of crabs that look exactly like Halloween moon crabs. Found in Northwestern South America, they were once thought to be Halloween moon crabs. 

However, in 2014, they were reclassified as a separate species — Gecarcinus nobilii. The two species look the same; they mainly differ in their geographic distribution. 

Halloween Moon Crab Temperament and Behavior

Understanding the temperament and behavior of Halloween moon crabs is essential for anyone looking to get one as a pet. Let’s delve into what you should expect from these colorful crustaceans.

Halloween moon crabs are shy and skittish

Halloween moon crabs are notably shy and skittish. They are not the kind of pets that enjoy being handled or touched.

In fact, handling can stress them out. They are more suited to being observed rather than interacted with directly. It’s important to respect their need for space and avoid unnecessary handling to keep them comfortable.

They are nocturnal

Halloween moon crabs are active at night. They spend their days hiding or burrowing and become active after sundown. At night, they come out to look for food and explore. 

This nighttime activity is a part of their natural behavior, as they prefer to move around and search for food when it’s cooler and darker, just like they do in the wild.

They are semi-aggressive and territorial

Halloween moon crabs have a reputation for being territorial and a bit on the aggressive side, especially the males as they get older. These crabs like their space, and they don’t usually get along with others of their kind.

Generally, males are more likely to show aggression and can hurt each other if put in the same tank. The females are usually calmer but still like having their own area and don’t always live peacefully with others.

If you plan to keep more than one Halloween moon crab, you might want to go with a group of females or one male with a female or two. 

But even then, you need to watch them closely to stop any fights, particularly when they’re molting and more vulnerable.

They like to climb, burrow and hide

Halloween moon crabs are natural climbers. They love to move around their environment skillfully. In the wild, you might find them up in trees or among bushes.

When you keep them in an aquarium, it’s good to have things like cork bark or fake plants for them to climb. This makes them feel at home and lets them do what they do naturally.

These crabs also like to dig and make burrows. They dig to find shelter and keep themselves moist in their natural home. If you have them as pets, they’ll need a thick layer of substrate in their tank so they can dig.

Halloween Moon Crab Lifespan and Health

Halloween moon crab on forest floor

The Halloween moon crab can live up to 8 years with proper care. Their lifespan largely depends on the conditions in which they live. 

However, despite their relatively long lives, some factors could shorten their life, such as the following:

  • Incorrect temperature and humidity in the tank
  • Not getting the right mix of food
  • Problems during molting
  • Inadequate space
  • Physical trauma from tankmates
  • Dehydration

By understanding and addressing these risks, you can significantly enhance the quality of life for your Halloween moon crab. 

Regular monitoring and adjustments to their habitat and diet, along with careful observation during their molting process, are essential practices for any crab owner.

Keeping Halloween Crabs as Pets

Owning a Halloween moon crab can be a rewarding experience. A part of the experience is creating a suitable living space, providing a balanced diet, and maintaining the proper temperature and lighting. 


A single Halloween moon crab needs at least a 15-gallon tank. If you’re keeping more than one, opt for a larger tank to prevent aggression between crabs. A secure lid is also important since they are known to climb out.

The tank’s substrate should be a mix of coconut fiber, peat, sand, and soil, at least six inches deep and kept moist. This setup allows the crabs to indulge in natural behaviors like digging and hiding.

Climbing structures such as branches, plastic plants, and pots are also a must, as these provide exercise and hiding spots for your crab.

Here’s a helpful video on setting up a simple Halloween moon crab enclosure: 

Halloween Moon Crab Basic Care

Diet and Nutrition

Feeding a Halloween moon crab is not complicated, but there are some key things to know to keep your pet healthy. 

Here’s what the diet of a Halloween moon crab should look like:

  • Fruits and vegetables: According to the Iowa State Insect Zoo, fish flakes, crustacean pellets, grapes, bananas, lettuce, broccoli, and spinach are best for moon crabs. Offer them a variety of fruits and leafy vegetables cut into manageable pieces.
  • Protein: Though mostly herbivorous, your crab will appreciate occasional protein. Offer small amounts of fish or peanut butter. Make sure these are plain and free from any seasonings or oils.
  • Calcium source: Calcium is crucial for their shell health. Add a piece of cuttlebone to the tank. Your crab will gnaw on this to get the calcium it needs.

Meanwhile, here are some tips on feeding Halloween moon crabs:

  • Portion size: A good rule of thumb is to offer food that is about the size of your crab’s shell. This helps prevent overfeeding.
  • Feeding frequency: Feed your crab once a day, preferably in the evening since they are nocturnal.
  • Removing unfinished food: Removing leftover food within 24 hours is important. This prevents the growth of mold and bacteria in the tank.
  • Water: Always provide fresh water in a shallow dish. They need this for drinking and also to maintain their gills’ moisture.
  • Variety is key: Rotate the types of fruits and vegetables you offer to ensure a balanced diet.
  • Avoid processed foods: Stick to fresh, natural foods. Processed human foods can contain harmful additives for crabs.

Feeding your Halloween moon crab correctly is straightforward once you get the hang of it. With a balanced diet, your crab will be a healthy and fascinating pet.

Fun Fact: Did you know that crabs consume their molted shells? They do this to reclaim essential calcium, which is vital for their growth and the strength of their new shells.

Temperature and Lighting

Creating a comfortable environment for Halloween moon crabs is straightforward once you know the basics of temperature and lighting.

Here’s a guide to help you maintain the right temperature:

  • Heating pad: Buy a reptile heating pad suitable for your tank size from a trusted pet store or online shop.
  • Placement: Put the heating pad under one side of the tank to create a warm and cooler area.
  • Setting: Adjust the pad to keep the tank between 75°F and 85°F, which is ideal for these crabs.
  • Monitoring: Use a digital aquarium thermometer to check the temperature regularly.
  • Adjustment: If the temperature is off, tweak the heating pad settings for consistency.

And here’s how to set up the lighting for your Halloween moon crab:

  • Bulbs: Choose red lights or low-wattage bulbs, as bright lights can stress these nocturnal creatures.
  • Light fixture: Get a fixture that fits the bulb and can be securely attached to the tank.
  • Placement: Install the light on the tank’s lid to provide indirect, dim lighting.
  • Schedule: Keep the light on for about 8 to 12 hours a day to emulate a natural light cycle.

By maintaining the right temperature and lighting, your Halloween moon crabs will have a habitat that keeps them healthy and active. Regularly monitoring and adjusting these conditions is key to replicating their natural environment.

Breeding Halloween Moon Crabs

Halloween moon crab on grass

Breeding Halloween moon crabs is highly challenging. These crabs have a complex life cycle in the wild, involving migration to the ocean, which is hard to recreate in captivity.

Here’s a simple guide to help you understand the process better:

Preparing for Breeding

  • Setting Up the Environment: Create a habitat that closely resembles their natural conditions. Maintain a proper temperature of 75 to 85°F and humidity above 80%. Use a tank of at least 15 gallons, equipped with both freshwater and shallow saltwater areas and a substrate over six inches deep for burrowing.
  • Choosing the Crabs: Select healthy adults, ideally with a shell size of 2 to 2.5 inches, to indicate maturity. Breeding is more likely to succeed with mature and robust individuals.

The Breeding Process

  • Conditioning Phase: Begin by feeding the crabs a nutritious diet that’s high in calcium and protein. This helps with egg development and keeps the crabs healthy.
  • Pairing Crabs: Carefully introduce a male and female crab in a neutral part of the tank.
  • Observing Mating Behaviors: Pay attention to their behavior, especially claw waving and touching. If you see any signs of fighting or aggression, separate them immediately.
  • Egg-Laying and Incubation: After mating, the female crab will carry the eggs. It’s important to keep the tank conditions steady during this time.
  • Larval Care: Once the eggs hatch, the baby crabs, or larvae, will need brine shrimp nauplii to eat. They pass through several stages in the water before they grow into juvenile crabs. Watch the water’s quality and temperature closely during this delicate stage.
  • Transition to Land: Gradually introduce the juvenile crabs to a mixed land and water environment as they develop.

Other Considerations

  • Survival Rate: It’s tough for the larvae to make it to the juvenile stage. This is mainly because their development stages are quite complex and require specific conditions.
  • Lighting: Keep the tank lighting dim, using low or red lights. This is important because Halloween moon crabs are active at night, and bright light can stress them out.
  • Social Structure: After breeding, house juveniles separately to prevent territorial disputes.

Breeding these crabs demands patience, a deep understanding of their lifecycle, and meticulous care. While challenging, success in breeding can be rewarding for dedicated enthusiasts. 

How Much Does a Halloween Crab Cost?

Halloween moon crabs are moderately priced pets. Generally, you can expect to pay between $5 and $30 for each crab. This price range varies depending on the size and age of the crab, as well as where you purchase it from.

If you’re looking to buy a Halloween moon crab, here’s a list of reliable places where they are currently available:

  • Backwater Reptiles – They offer a variety of Halloween moon crabs with a promise of 100% live arrival. Check out their collection for diverse options​​.
  • Underground Reptiles – This online store sells field-collected Halloween moon crabs. You can buy individual crabs or a set of three.
  • Big Apple Pet Supply – Known for selling a wide range of exotic pets, this store also offers Halloween moon crabs at around $29.95 each. They also provide specialized shipping to ensure the safe delivery of these crabs​​.
  • Aquarium Fish Depot – Located in San Diego, California, this store offers Halloween moon crabs for a price of $19.99. They also have other aquatic and exotic animals on their online store.
  • LLLReptile – This online store regularly updates its stock of Halloween moon crabs. You also have the option to subscribe to their mailing list to get notified when new crabs are available​​.

When buying a Halloween moon crab, remember that the cost of the crab is just the beginning. Setting up a suitable habitat and ongoing care will also add to the cost.

To cut down on expenses, you might also consider catching a Halloween moon crab yourself. I saw this myself in one of Costa Rica’s rainforests near the beach. 

The locals there showed how they catch these crabs using simple methods and makeshift traps. But remember, it’s important to know and follow the local wildlife rules before you try to catch a crab and take it home.

Recommended Tankmates for a Halloween Crab

Vibrant Halloween moon crab on the ground

When picking tankmates for Halloween moon crabs, it’s important to know that they like to be alone and can get territorial. 

Usually, it’s best to keep them by themselves because they might fight with others, especially when they’re molting. But if you really want to add other creatures, you need to plan carefully and keep a close watch.

If you want to keep more than one Halloween moon crab in a tank, here are some possible setups:

  • One male with several females: This helps avoid fights between males. Make sure your tank is big and watch them closely, especially when it’s breeding time.
  • Group of females: Female crabs are usually not as aggressive, but they might still fight over space. Make sure there’s enough room and places for them to hide.

You can also try adding other creatures in a tank with your Halloween moon crabs, but caution must be exercised:

  • Big snails: They can usually live with the crabs without any problems.
  • Strong shrimp: Some types of big shrimp might be okay if they can stay out of the crab’s way.
  • Peaceful fish: Choose fish that swim in different parts of the tank where the crab can’t get to them.

Even if these combinations work, you should always watch how your crab gets along with your chosen tankmates. Remember, the tank needs to be big enough for each animal to have its own space.

Frequently Asked Questions

Halloween moon crab partially covered in sand

Are Halloween Crabs Edible?

Yes, Halloween moon crabs are edible. Despite their bright colors that may give off a toxic vibe, they can be consumed.

Are Halloween Crabs Poisonous?

No, Halloween moon crabs are not poisonous. They are safe for humans if the need arises to handle or consume them.

Can Halloween Crabs Live in Freshwater?

Halloween moon crabs need both freshwater and saltwater to thrive, as they are terrestrial and cannot live in water alone.

Why Do Halloween Crabs Need Saltwater?

Halloween moon crabs need saltwater because their natural habitat is near the ocean, and their larvae develop only in saltwater environments.

Hopefully, this guide has taught you a thing or two about these unique crabs. Are you getting one soon? Share with us your thoughts and comments below about the fascinating Halloween moon crab!

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