Harlequin Crab (Cardisoma armatum)

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Harlequin Crab

Cardisoma armatum-1141.jpg
Harlequin Crab

Cardisoma armatum

38 Litres (10 US G.)

7.6-10.2cm (3-4 ")


7.2 - 8.0

23.9-29.4°C (75 -85 °F)

8-12 °d

1:1 M:F

Pellet Foods
Other (See article)

2-5 years

Alternative names[edit]

Harlequin Crab, Rainbow Crab, Patriot Crab, African Moon Crab, Soap Dish Crab, Moon Crab, Columbian Crab


Cardiosoma armatum


Males have a narrow tail flap, while females are wide.


They can reach a maximum carapace size of 20cm across, though they will grow to their surroundings so captive individuals rarely reach this full length. They are usually brighter when they are young, with the colouration fading as they age. They typically have a blue/violet carapace, red legs, and white claws.

Tank compatibility[edit]

This is a territorial Crab which is best in species tank, one to a tank, although a male/female pair may work provided the tank is large enough. It will attempt to eat fish.


They are true scavengers and opportunistic predators; the majority of their diet consists mostly of fruit, vegetation, and carrion. They will eat whatever they can find (dead or alive) but will never miss an opportunity to eat a smaller crab, freshly moulted crab or crayfish and generally anything that can be caught and held onto long enough to eat.

Feeding regime[edit]


Environment Specifics[edit]



The general behavioural patterns of this crab are similar to most others in the aquarium environment but due to sheer size they are prone to eat smaller crabs, crayfish, smaller fish and generally anything they can find. They do well to have at least one perch above water per crab (or a larger shared one) where they will carry food off to eat often. These crabs should be treated as an aggressive pet.




External links[edit]