The Red Apple Crab (Metasesarma aubryi) is a rather uncommon and unknown crab in the hobby. These crabs are not fully aquatic, on the contrary, they are terrestrial crabs. It makes them an excellent choice for a paludarium setup.
One of the great things about these crabs is that they are very easy to care for, which makes them great for those keeping crabs for the first time. In addition, they will not take up much space either because of their small size.
Nonetheless, while Red Apple crabs are quite hardy, they do require some unique conditions in order to thrive in captivity.
Therefore, to make things easy, I made sure to cover all the essentials of Red Apple Crab care in this guide. I will explain in detail all the necessary aspects of their habitat, tank setup, diet, tank mates, and other helpful facts!
Quick Notes about Red Apple Crab
|Name||Red Apple Crab|
|Scientific Name||Metasesarma aubryi|
|Tank size (minimum)||5 gallons (~20 liters)|
|Size (carapace)||2.5 – 4 cm (1 – 1.6 inches)|
|Size across the leg span
||7 – 10 cm (3 – 4 inches)|
|Optimal Temperature||71 – 79 °F (22 – 26 °C).|
|Water type||Freshwater bowl|
|Moisture||70% and higher|
|Substrate||4 – 5 inches (10 – 12 cm)|
|Diet||Mostly herbivore /omnivore|
|Life span||up to 6 years|
|Color Form||Vivid red to dark bluish or purple with orange edges|
Habitat of Red Apple Crab
These crabs originated from the lands of Sulawesi and Java Island in Indonesia.
Nowadays its geographical distribution is much wider, they can be found in New Caledonia, Taiwan, Gulf of Thailand, Sumatra, New Guinea, Rotuma, Morotai Islands, and the Mergui Archipelago.
Their habitat is areas nearby the river stream in the dense tropical forest. Metasesarma aubryi species prefers densely wooded areas, close to watercourses, shady areas, where they can dig and hide.
Description of Red Apple Crab
Red Apple crabs are relatively small. The average size (shell width) of the adult crabs is only about 2.5 – 4 cm (1 – 1.6 inches) long. To be precise, across the leg span, they barely reach 7 – 10 cm (3 – 4 inches).
Their name can be misleading. Not all Red Apple crabs have a vibrant red coloration. The carapace color can also vary from dark bluish to purple with orange edges.
They have red round claws, yellow to green eyes, and brown legs.
Many crabs of Metasesarma aubryi species have a yellow horizontal line on the left and right sides of the frontal region between the eyes of the carapace. However, this is not a distinctive feature of this species.
Interesting fact: In Indonesia, Red Apple crabs are also called Chameleon crabs due to their ability to display different colors depending on the crab’s mood and the surroundings of the environment.
Lifespan/Longevity of Red Apple Crab
Currently, there is no data available on the average or maximum lifespan for Red Apple crabs in the wild. However, they can live for 3 – 4 years, and some specimens for even more than 5 – 6 years in captivity, if appropriately cared for.
Behavior of Red Apple Crab
Red Apple сrabs are nocturnal animals. The pick of their activity starts at dusk and gradually stops during the night, before sunrise.
This nocturnal behavior is not uncommon for grazing invertebrates and is mainly associated with attempting to avoid visual predators whilst feeding. However, it does not mean that you will never see them in a day time. They are simply less active during this time.
Although Red Apple crabs are not completely harmless, they are still considered social. The bigger their colony, the safer they feel and more confident they act in the tank.
At the same time, they also have complex territorial interactions. Therefore, overcrowding will definitely not end well.
Do not keep them with other crab species. They do not like intruders. For example, they are a little bit bigger and more aggressive than Geosesarma species (such as Vampire Crab, Tangerine-head crab, etc.) and Marble crab (Metasesarma obesum). So, it would not be a good idea to keep them together.
Red Apple crabs are not destructive, however, be ready that they will dig some small dens in the substrate or move small objects in your tank.
Feeding Red Apple Crab
Red Apple crabs are natural-born scavengers.
In nature, this species mainly feeds on vegetable debris, mainly roots, stems, and supplemented with dead insects, tadpoles, worms, larvae, etc. Basically, they are omnivores and can eat almost anything.
In captivity, for the best growth, Red Apple crabs need a good mix of meats and vegetation, where their feeds should contain protein at a level of about 20 – 30% of the diet.
Foods Red Apple crabs will enjoy (examples with links to check the price on Amazon), for example:
- Vegetables (like broccoli, cabbages, carrots, cucumbers, lettuce, corn, spinach, peas, squash, leafy greens, etc.).
- Fruits (Apple (only sweet), banana, pearl, melon, mango, etc.)
- Shrimp pellets.
- Shrimp Granules.
- Fish food (TetraMin® flakes, etc.)
- Shrimp food (Hikari’s crustacean food like Hikari Shrimp Cuisine, Algae wafers, Brine shrimp, etc. )
- Frozen blood worms.
- Detritus worms.
- Brine shrimp.
Leaves (for example, Almond leaves, dead beech, oak leaves, etc.) should always be on the menu, as they feed on these and require the detritus from the leaves.
Do not ever give your Red Apple crabs:
- sweets (like candy),
- flour (including bread).
It is not good for their digestion and health.
- You can also read my articles:
How often should We Change the Food?
You can leave their food for 24 hours before removing it. Leaves can be left for several days in the tank.
Just make sure that whatever Red Apple crabs do not consume in one day is removed to prevent moles.
How often should We Change the Menu?
Do not give them the same food for weeks. Ideally, you need to change their diet at least every week.
Do Red Apple Crabs Need Calcium?
As with all crustaceans, calcium is a crucial component of a Red Apple Crab’s exoskeleton and overall health.
Calcium can be found in kale, broccoli, spinach, cuttlebones, eggshells, figs, wonder shells, oyster shells, seaweed, seeds, insects, etc.
Always keep a small piece of Cuttlefish bone in their enclosure. Red Apple crabs need calcium. Supplement their diet and make sure they get enough calcium (for the exoskeleton) by regularly feeding specialized invert foods.
|I highly recommend reading my article “How to Supplement Shrimp and Snails with Calcium”.|
Cuttlefish bones – link to check the price on Amazon.
Keeping and Housing Apple Crab
Luckily, Red Apple crabs are very easy to care for even for beginners.
However, if you want to have a happy and healthy crab as long as it is possible, it is important to give it everything it needs, including proper care.
Red Apple crabs like to have their own space to roam around, as well as a varying amount of terrain to hide in and escape to from things like unwanted attention or sunlight.
That is why the minimum recommended tank size for a few Red Apple crabs (1 male and 1 or 2 female) is a 5-gallon (20-liter) tank.
Keep in mind that overcrowding is the main source of stress for crabs. As a result, it can lead to health problems and aggression. This is particularly important when you have more than one male, as they are more aggressive than females.
For a bigger colony of Red Apple crabs, you will need to add at least 1 to 2 more gallons (or 4 – 8 Liters) of tank space per additional crab.
Whatever size of tank you go with, make sure it has a stable lid! Like all crabs, Red Apple crabs are excellent escape artists! They can and will try to climb out of their tank when given the chance.
We need to mimic their habitat (dense tropical forest). Therefore, the substrate should be moistened to sandcastle consistency at all times. It will also help you to maintain a proper level of humidity.
Note: If your Red Apple crabs often visit water bawls, it can be a sign that the substrate is too dry.
In addition, sometimes, Red Apple crabs can burrow in the substrate when they start molting.
The substrate in the tank can be made of peat, earth, sand, or sand-earth mixture to nibble at and excavate in. The substrate should be moist enough so when you squeeze it holds its shape.
From the practical point of view, coconut fiber best of all of them. It shows the best results for the more humid-loving creatures.
Tip: You can test the consistency of the substrate with a pencil. Stick it all the way down and pull back up. If the tunnel does not collapse, your substrate is fine.
How Deep should be the Substrate in Red Apple Crab Setup?
In the wild, these crabs are known to burrow in muddy substrates up to 4 inches (10 cm) deep. However, these burrows are always above the water line.
Substrate options (check the price to Amazon):
Land vs Water Ratio
Red Apple crabs are not aquatic; they are terrestrial crabs. Therefore, the land area should take at least 90% of the space in your tank or even more.
Water Bowl and Water Type
Because Red Apple crabs are land crabs, they cannot even survive in freshwater for a long time. They will drown.
However, they should have a suitably sized bowl of water available to them 24/7. The water bowl should be big enough for the Red Apple crabs to fully enter it.
Do not forget to put a variety of surfaces (rocks, driftwood, etc.) for them to get out of the water.
What type of water do Red Apple crabs prefer?
These crabs need only freshwater. There is no need to add an additional bowl with saltwater.
Note: They use saltwater only for reproduction purposes when they are releasing eggs.
It is important to provide your Red Apple crabs with chlorine and fluoride-free water, as these things are toxic to them. Let it age for 24 hours before using it.
You can also use a water conditioner for their water. For example, Seachem Prime (link to check the price on Amazon) will remove also toxic gases, bind to heavy metals, any ammonia, nitrites, or nitrates present for up to 48 hours.
Another option is to give them bottled spring water.
As Red Apple crabs prefer a warm and humid environment, the range of optimal temperatures is anywhere between 71 – 79 °F (22 – 26 °C).
Red Apple crabs are poikilothermic, which means that their body temperature completely depends on the temperature in their surrounding environment.
So, any big fluctuations in temperature or a cold day can drastically reduce the warmth in a tank that can potentially cause your crab to suffer from temperature shock.
In this case, it can be a good idea to have a heat mat under the tank to keep the tank warm.
Tip: The heat pad should cover 1/3 (or less) of the tank so that Red Apple crabs can move from warmer to colder places anytime they want. This allows your crabs to regulate their body temperature to their needs.
One of the most popular heaters – Zoo Med Repti Therm Under Tank Heater (check the price on Amazon).
Humidity levels are very important. Red Apple crabs need moist, and humid air to breathe and molt properly.
The humidity level should be between 70-90%.
Humidity and Thermometer (links to Amazon):
- Zoo Med™Reptile Terrarium Digital Thermometer,
- Zoo Med Labs Digital Thermometer Humidity Gauge,
- AcuRite 00613 Indoor Thermometer & Hygrometer with Humidity Gauge
How to keep the tank humid?
- Keep the substrate moist. Fill a plastic spray bottle with dechlorinated water and spray this over the substrate side of the tank at least 2 times a week.
- Provide water for your Red Apple Evaporation will automatically increase the humidity level.
- Use a glass top. It will increase the evaporation effect.
If your humidity levels stay too high or too low, it can be fixed by adding more moisture, less ventilation, or by adding more ventilation.
This is normally a trial and error process, so expect it to take some adjusting to get it perfect.
Important: Be careful and avoid over humidifying as a saturated substrate can cause mold and infection.
Red Apple crabs are nocturnal animals.
Lighting should be adapted to the needs of plants in the paludarium or terrarium.
Decorations and Hiding Spots
It is important to minimize stress to your Red Apple crabs by giving them a lot of places to hide.
This is also crucial for the molting process!
For that ceramic flower pots, flat stones, PVC pipes, and pieces of bark, driftwood will do the job. You can add some rocks, plastic balls, plastic tunnels, crab huts, plastic plants, fish netting, and other decorations to enrich the environment.
These crabs love climbing!
Plants are good for their setup too. Red Apple crabs usually do not show any gastronomical interest in live plants.
In addition, crabs will benefit from live plants by collecting bacteria and microorganisms off them.
Red Apple Crab and Molting Cycle
The molting process (the molt cycle) is the most important part of the Red Apple crab’s life.
Basically, this is the process by which a crab grows. It involves shedding of the exoskeleton and for a short time afterward, the crab cannot move until it regains muscle control and the new exoskeleton hardens up.
This process has 4 phases:
During pre-molting periods, most metabolic activities are reduced to a minimum. Red Apple crabs stop eating and become very lethargic. They need darkness, moisture, and heat to successfully molt.
The pre-molt stage terminates with the molting shedding of the old shell. Depending on how old it is, it usually lasts from 10 to 30 minutes.
The post-molt is another critical phase in the molting cycle of the Red Apple crab. They are vulnerable and helpless during and after molting, so it is necessary for them to go into hiding and not reappear until the process is complete and their new carapace has begun to harden.
The inter-molting stage is the last and the longest stage. It is a period when the Red Apple crab is resting between the molting cycles.
- NEVER disturb them when they are about to molt. Even if you have not seen your Red Apple crab for a few days in a row! Give it time. This is the most stressful moment in its life.
- Keep putting and replacing food in the tank! You never know when they can come up from the molt.
- Keep giving them calcium-rich food.
- Also, do not remove the old exoskeleton from the tank. It contains lots of minerals and your Red Apple crab will eat it later.
For more information, read my article “Crabs and Molting Process”.
Rules: How to Care and Handle Red Apple Crab:
- Red Apple crabs are not pets you can play with. Do not take them out just because you want to.
- Red Apple crabs should never be lifted up by their legs or claws! They can lose a limb by autotomy.
- Do not leave uneaten food for too long. It can cause smell and bacteria in their enclosure.
- Decorate the enclosure with as many things as you please because Red Apple crabs love to climb and hide.
- The substrate should be based on sand and Eco-earth to give them a homely feeling.
- Humidity and temperature are extremely important for keeping Red Apple crabs.
- Make sure the lid of the tank is closed tightly so that they cannot escape it.
Red Apple Crabs – Male and Female Differences
Red Apple crabs are sexually dimorphic. There are a few indicators that give away the gender of the animal.
- Males are a little bit bigger than females and have larger claws.
- Abdomens. We can differentiate the gender by the shape of their abdomens. Males have a narrow and slimmer plate (triangular) while females have a broad plate on their belly.
- Coloration and Size. Males have more vivid colors.
Note: The last methods are not completely reliable, especially after molting when their color becomes more intense.
Breeding Red Apple Crabs
Unfortunately, it is close to impossible to breed them in captivity. So far, I have not o heard or read any success stories.
Currently, the pet industry completely depends on wild-caught species.
In the wild, Red Apple crabs migrate to the ocean to release eggs that hatch into planktonic marine larvae. Each female may produce thousands of eggs, however, only a small fraction of them eventually metamorphose and crawl back onto land.
The breeding season of Metasesarma aubryi is variable, depending on the beginning and ending of the rainy season, between May and November.
They release larvae during the last quarter of the lunar cycle. In southern Taiwan, the migration of crabs commences after midnight from the highland forest until the time before dawn for larval release.
Red Apple Crabs and Suitable Tankmates
These crabs can be kept in a group relatively safely, but only under several conditions:
- Males to females ratio (1:3). In the small enclosures, Males, in particular, are extremely likely to fight.
- The tank should have lots and lots of hiding places.
In a paludarium setup, it is possible to keep dwarf shrimp and fish with them. Red Apple crabs do not spend a lot of time in the water in any case.
Bad Tank Mates:
- Any Crayfish species.
- Other crab species.
Red Apple crabs are excellent scavengers and easy to care for once you understand their needs and preferences.
Having them as pets can be exciting but it is one big responsibility. After all, they can live for several years.
These little crabs are cute, unique, and simply amazing! They are very interesting to watch! The only problem is that they are fairly new to the hobby and pretty rare in the pet trade.
7 thoughts on “Red Apple Crab – Detailed Guide: Care, Diet, and Breeding”
Hi a great read.
I have kept what I believe are the red apple crab for a few months donated to me by someone who could not care for them any longer.
I have a fairly large female who is bursting with eggs I know they are almost impossible to breed which I believe is more about feeding the young do you have any advice?
Hi Dave Ayres,
I am not sure what kind of advice you expect me to give you.
During my research, I could not find any detail that can help us. There was no even information on the stags of marine larvae and how long they last.
It is true that breeding Red apple crabs is a monumental task and way harder than, for example, breeding Amano shrimp (This species also requires saltwater).
Nonetheless, if you really want to try it, I’d start with the same setup as for the breeding Amano shrimp, you can read it in my article.
Greetings, I am the very first person to make a care guide for these guys and I just want to say thank you for making this guide! It helps a lot to spread this information as I believe these guys are the better alternative to Hermit crabs as they are harder to care for.
As for breeding, I tried before when I had a gravid female, I decided to make a temporary completely seawater tub unlike the Amano brackish water setup and I got fairly far, the female, during the early parts of the morning like around 2-3 AM, went into it, shaked up and down vigorously like how Christmas Island crabs do and deposited the eggs. Afterwards she promptly got out of the tub and went straight for the freshwater tub.
The eggs hatched a few days later and they looked like microscopic versions of mosquito pupae, not larvae, and I fed them powdered spirulina, but mostly just the biofilm in the tub already. I think if I fed them the powder when they are a few days old they can’t eat it cause I heavily relied on biofilm to feed them
I still don’t know what I did wrong but they all died after a couple of weeks. This all happened a year ago and I don’t have nearly as many red apple crabs but I will try again whenever I have multiples again
Thank you for the feedback!
I do hope that eventually, somebody will find a way to breed them and create the proper protocol, so they will not be taken from the wild anymore.
Have you tried marine phytoplankton instead spirulina?
I’ve just started my dissertation for my Marine Biology and Coastal Ecology degree. For my project I am attempting to study the captive breeding of M. aubryi.
You appear to of got futher than anyone else I have seen online, would you please be able to answer a few questions for me on the conditions that you used and on the process?
1. Do you know what zoae stage you achived?
2. What salinity/temperature did you use?
3. How deep was your spawning tub?
I’d like to add females can apparently retain sperm for almost a year if not longer. The male I had with my female died last year and yesterday evening, I found her berried. I suspected something was up because she actually dipped into the water.
I have also found she has always been extremely active during the day when she’s berried.
Where can these crabs be purchased in the USA in 2022? It seems any online aquarium that lists them has them out of stock. This seems to be the case for all terrestrial or semi-aquatic crabs except hermit crabs and vampire crabs.