Today I would like to talk about one of the most beautiful crabs you can find in pet stores – Tangerine-head crab (Geosesarma krathing). These absolutely gorgeous and beautiful crabs are sure to attract attention in any paludarium.
Although Tangerine-head crabs are not very common in the aquarium trade, they are one of the best terrestrial crabs you can wish for. Why? Because they are peaceful, hardy and easy to care for. In addition, they can breed in captivity! In my opinion, Tangerine-head crabs are some of the most underrated crabs in the aquarium hobby.
I need to start off by saying that knowledge of these crabs is scanty and little is known concerning details of their ecology. Basically, it is going to be one of the first guides about his species. Nonetheless, I have done my best to gather all information (including official studies) about the proper care of Geosesarma krathing species.
Fact: These crabs were described and classified by scientists in 1992 and in 2007 Tangerine-head crabs appeared in the pet trade for the first time. However, the funny this is that no one knew where they come from.
Quick Notes about Tangerine-head Crab
||Orange Vampire Crab, Red Tomato Crab, Indonesian Freshwater Crab
|Scientific Name||Geosesarma krathing|
|Tank size (minimal)||5 gallons (~20 liters)|
|Size of the carapace||1 – 1.5 cm (0.4 – 0.6 inches)|
|Size across the leg span||3 – 4 cm (1.2 – 1.6 inches)|
|Optimal Temperature||22 – 24°C (~71°F – 75°F)|
|Aquarium type||Paludarium (aquarium that has both terrestrial and aquatic elements (freshwater)|
||75% and higher|
|Nitrate||Less than 20 ppm|
|Life span||up to 2 years|
|Color Form||Orange with yellow eyes|
Why are They Called Geosesarma krathing?
The species is named after the area where it was collected, Krathing. The name is to be used as a noun in apposition.
Natural Habitat of the Tangerine-head Crab
Tangerine-head crabs (Geosesarma krathing) originate from eastern Thailand in the Chanthaburi Province, near the Cambodian border.
These little crabs live in forests at and near the bank of this province’s main river. Tangerine-head crabs are also often referred to as tree-climbing crabs because of their ability to climb bushes and trees along the riverbank.
These crabs do not depend on saltwater for development in any stage of their life.
Description of the Tangerine-head Crab
The Tangerine-head crabs are a small, colorful, semi-terrestrial species. The average size (shell width) of the adult crabs is only about 1 – 1.5 cm (0.4 – 0.6 inches) long. To be precise, across the leg span, they barely reach 3 – 4 cm (1.2 – 1.6 inches).
These brightly colored decapods have earned this common name from their bright orange to red coloration of the carapace and claws.
Like many crabs of their genus, Tangerine-head crabs’ claws do not open very wide. They are more suited to picking up detritus or move soft soil.
They do not live long. In the aquarium, the life span of Tangerine-head crabs is usually 1.5 – 2 years under optimal conditions.
Behavior of the Tangerine-head Crab
Tangerine-head crabs are shy and nocturnal. Nonetheless, from time to time you will also see them at dusk or even during the day.
They are also pretty active and social. Tangerine-head crabs are not territorial, like most crab species. There will not be fights for territory and dominance. On the contrary, Tangerine-head crabs enjoy the company of their species members. It makes their life richer and less stressful. Larger colonies often have more active members, that can be seen venturing out from hiding and showing off more often.
However, they do not like intruders of other crab species and can fight with them Basically, this is a good example of a species competition in nature.
When threatened, or startled Tangerine-head crabs will do their best to escape, or take cover. They are entirely defenseless.
Although they can often dig into the substrate, they are not a burrowing genus of crabs. Instead of sitting in the dens, they usually prefer to climb everywhere. Tangerine-head crabs are active on the surface.
Feeding Tangerine-head Crabs
Tangerine-head crabs are predominantly omnivorous creatures, meaning that they can just eat whatever is nearby.
According to the study, biologists found in the stomach of these crabs:
– 77 % – soil/substrate,
– 13 % – wood chips,
– 6% – percent leaves,
– 3 % – roots,
– 1 % insect and flower pieces.
As we can see, Tangerine-head crabs prefer detritus and plant parts as their main diet. However, they are not complete vegetarians. We need to keep in mind that the diet can also change depending on the season.
Foods Tangerine-head Crabs will enjoy (examples with links to check the price on Amazon)
- 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
- Vegetables like spinach, peas, squash, leafy greens, etc.
Ideally, you need to give them different types of food to get all the necessary microelements. When you decide to give Tangerine-head Crabs vegetables, you need to do it the safe way. Read my article “How to Blanch Сucumbers and Zucchini for Shrimp, Snails and Fish the Right Way”.
Add Almond leaves, dead beech, or oak leaves regularly as they feed on these and require the detritus from the leaves. Read my article “Indian Almond Leaves and Alder Cones in a Shrimp Tank”.
Tangerine-head Crabs and Molting
Like all crustaceans, Tangerine-head Crabs need to molt to grow. With time, as they outgrow the existing shell (exoskeleton), they begin to shed their shells off. This process is called molting.
Once that outer shell is shed, it is common to think that the crab is dead, but it isn’t. During this period of time and right after it, the Tangerine-head Crabs will hide until a new shell becomes hard (mineralized).
Molting is the most vulnerable process in the lives of any crustaceans. They are extremely vulnerable and can be easily hurt. To prevent it from happening, you will have to provide a lot of hiding places or other crabs can eat a molted one.
Tip: Do not throw away old exoskeletons. They contain lots of minerals and crabs will gladly eat them after some time. Like all snails, shrimp, and crayfish, crabs, also require a lot of calcium for their exoskeleton. You can learn more about it in my articles:
Keeping and Caring for Tangerine-head Crabs
These carbs are hardy by nature. However, they still have some specific requirements if you want to create an ideal environment for them. In general, Tangerine-head Crabs are highly suitable for keeping in paludariums.
The minimum recommended tank size for Tangerine-head Crabs is a 5-gallon (20-liter) tank. The bigger the tank, the better it may be to setup paludarium with diverse areas for them to dwell.
Tip: These crabs are great escape artists. So, a tight-fitting lid is essential.
Land vs Water Ratio
Even compared to species such as Vampire crabs, Tangerine-head Crabs seem to have a clear preference for terrestrial areas. It is absolutely not enough to put there just rocks and driftwood to climb and sit on. The land area should take 90% of the space or more.
According to the observations, adult Tangerine-head Crabs spend most of their time on land. Only baby crabs use water.
Water Bowl and Water Type
I have already mentioned before, in some of my guides, that in paludariums, instead of creating a complex tank setup, you can use a big water bowl. The only thing that you need to keep in mind – this bowl should be big enough to completely submerge your crabs.
Tangerine-head Crabs cannot stay in water for a long time. They will drown. It is crucial to provide a variety of surfaces for them to get out of the water.
Of course, I understand that water bowls may not look great in the setup but they have huge advantages:
- All water changes will be very easy and simple.
- There will be no need to use any filters to maintain cleanliness and prevent toxicity!
Regarding the type of water. Tangerine-head Crabs need only freshwater. If you use tap water, add Seachem Prime (link to check the price on Amazon) to remove chlorine, chloramine. This water conditioner will also bind to heavy metals, any ammonia, nitrites, or nitrates present for up to 48 hours. Consider Prime as your additional safety net.
Temperature and Humidity
The range of acceptable temperatures is anywhere between 64 – 86 °F (18 – 30 °C) with around 71 to 75 (22 – 24C) being optimal.
As a matter of fact but Tangerine-head Crabs are pretty resilient to humidity fluctuations. This is another reason why they are easy to care for. However, for optimal conditions, it is still recommended to keep the humidity around 75% or higher.
The substrate in the tank should be made of peat, earth, sand, or sand-earth mixture to nibble at and excavate in. Ideally, the land portion of the setup should be developed to reflect the rainforest. Personally, I find coconut fiber best of all of them. It shows the best results for the more humid-loving creatures. Make it moist enough so when you squeeze it holds its shape.
Add some leaves and pieces of bark on the soil, and include some plants.
No special requirements. Lighting should be adapted to the needs of plants in the paludarium.
Decorations and Plants
Tangerine-head Crabs will appreciate all types of leaves, rocks, wood, plants, PVC pipes, etc. in your tank.
It is absolutely safe to keep this species with any type of plant. Tangerine-head Crabs do not eat healthy plants and can, therefore, be kept in beautifully planted paludariums. Even more, they will benefit from live plants by collecting bacteria and microorganisms off them.
Note: Tangerine-head Crabs are terrestrial in habits and DO NOT require water acclimation.
Do not forget that Tangerine-head crabs also need stable humidity around 75% or higher. This is one of the reasons why people fail to keep them.
Tank Equipment (links to check the price on Amazon)
Determining Gender of Tangerine-head Crabs
Tangerine-head crabs are sexually dimorphic. Although it can be difficult to sex them because of their small size. We can still determine it externally:
- Abdomens. You can differentiate the gender by the shape of their abdomens. Males have a narrow and slimmer plate while females have a broad plate on their belly.
- Claws. Males also have larger and sometimes brighter claws. Females have smaller (about half that size) claws.
Note: The size of the crabs cannot be used as a reliable way to sex them. Unlike most crabs, where males are bigger than females, in Geosesarma krathing species, they are the same size. Even more, fully-grown females can be a few millimeters bigger.
Tangerine-head Crabs and Mating
The mating process is quite simple. If a female is interested in mating, she will allow a male to approach and flip her upside down. After that, the male wrap himself around her to fertilize.
The typical size at maturity of this species is about 8 – 10 mm (~0.3 – 0.4 inches).
Breeding Tangerine-head Crabs
In nature, the reproductive season of this species is being from January to April.
After mating, Tangerine-head Crabs females keep fertilized eggs at the underside of the tail until they hatch 2 months later. Before hatching, females become more secretive and start hiding almost all the time.
The average clutch size is 50 eggs. Female fecundity increases with body size.
Tangerine-head Crabs have direct development (no larval stages). Females give birth to live, fully formed miniatures of the adult Tangerine-head Crabs. Freshly hatched young crabs are very small and cannot live separately from the mother.
Baby crabs spend with the mother several weeks until they start an independent life. Once it happened it is advisable to separate adult crabs from the baby crabs by putting them in a rearing container. It will reduce potential cannibalism. Otherwise, only a small number of baby Tangerine-head crabs will reach the adult stage.
Unlike adults, the young crabs spend most of their time in or near the water, becoming proportionally more terrestrial as they mature.
Note: Keep in mind that young crabs can also become prey to the siblings during the molt. So, it is absolutely crucial to have as many hiding places as possible. Ideally, you should also separate them by size.
Tangerine-head crabs and Suitable Tank Mates
Tangerine-head crabs are social animals that do well in a community with their own kind. Therefore, if you decide to keep different species of Geosesarma (Red Devil crabs, Vampire crabs, etc.) or Metasesarma (Marble crabs or Red Apple crabs) in the tank, be ready for conflicts.
If paludarium size allows it is possible to keep dwarf shrimp and fish with them. They are generally non-aggressive, and many aquarists keep them perfectly safely alongside adult shrimps and snails. However, there is a risk that crabs can catch baby shrimp from time to time.
Bad Tank Mates:
- Larger or aggressive fish.
- Any Crayfish species.
- Other crab species.
Tangerine-head crabs are one of the smallest semi-terrestrial crabs that can be finally maintained in a small paludarium (aquarium). They are excellent scavengers and easy to care for. They do become less shy over time. All in all, this is an ideal invertebrate for a nano tank.
- Vampire Crab – Detailed Guide: Care, Diet, and Breeding.
- 7 Freshwater Crabs For The Tank.
- Difference between Aquarium, Terrarium, Riparium, and Paludarium?
- How to Set up Paludarium
- On a new species of Geosesarma de Man, 1892 (Crustacea: Decapoda: Brachyura: Grapsidae) from Chanthaburi Province, eastern Thailand. K.L. Ng & P. Naiyanetr. Zool. Med. Leiden 66 (34), 31.xii.1992:449-452,1 fig.— ISSN 0024-0672.
- “Preliminary study of biology and ecology of tree-climbing crab (Geosesarma krathing Ng and Naiyanetr 1992) (Crustacea: Brachyura: Grapsidae). The Proceedings of the 44th Kasetsart University Annual Conference 30 January–2 February 2006. Kasetsart University, Thailand. D
- Dost, U. 2008. “Erste Erfahrung mit der Aufzucht der Mandarin und der Vampirkrabbe.” DATZ 61(3):72–73.