Marine Invertebrates

Fiddler Crab

  • Scientific name: Uca Tangeri
  • Common name: Fiddler crab, claw crab
  • Aquarium size: 200 to 300 liters
  • Temperament: Calm
  • Temperature:  Between 24º and 26ºC
  • pH: Between 7 and 8.9
  • Diet: Omnivores
  • Length: 2.5 to 4 cms


The fiddler crab is a crustacean suitable for a marine aquarium , which replicates a tropical biotope and which has something to do with the areas closest to the coast.
It has a good number of common names in addition to fiddler crab, which is how it is known around the world: fiddle crab, mouth crab, claw crab, claw crab, mouthpiece, or skipjack are other equally popular names.
Its name «fiddler crab» is due to the fact that it has a hypertrophied claw, which moves in a rhythmic back and forth movement, reminiscent of the movements of a violist.
It is also true that within the fiddler crabs, there are different species: Uca Tangeri, Uca Pugnax… The one that most defines the species, for my taste is the Uca Tangeri, which is the largest of the genus Uca.


If something distinguishes the fiddler crab at first glance , it is a hypertrophied claw, which does not stop growing in the male, and for that reason it is larger than the other.
This clamp is used both for courting females, for fighting between males or to ward off predators.
It is possible that during your life, you may lose your hypertrophied forceps due to your use of it . In these cases, the smaller clamp begins to grow and the lost clamp develops again, but stays small.
The Uca have three well differentiated parts, on the one hand the head, on the other the thorax and finally the legs.
It has four pairs of legs that help it move, and two other legs, which we all know as pincers, although their scientific name is chelicerae.
The chelicerae in turn are made up of two fingers, one of them fixed and the other mobile, presenting the typical shape of all crabs «in pincer».
It has ocular peduncles, at the end of which are the eyes, with which it manages to have a very wide field of vision. Between the eye peduncles, small antennae appear, which it uses as a tactile organ.
Its usual color depends largely on the species and the place it inhabits . You can find very brightly colored fiddler crabs, ranging from purple to black.
It has the ability to change color under certain circumstances., as they are the passage from day to night, being in the presence of predators, in the mating season, even due to the change of season. The forceps have an orange-brown color, in some cases yellow or whitish.
In this species the sexual dimorphism is evident, the male has a hypertrophied claw, while the female has both claws of equal size.
Female fiddler crabs also have an oval abdomen, while males have a triangular shape.

Distribution and habitat

The fiddler crab is widely spread along several tropical coasts, but Uca Tangeri has a localized distribution from southern Portugal to southern Angola, an area corresponding to the eastern Atlantic.
Its natural habitat is very diverse thanks to its power of adaptation, it is possible to find it on beaches, mangroves, wetlands, in estuaries and the mouths of some rivers , so under certain circumstances, it can live in fresh water.

Aquarium conditions

They need a large aquarium of about 300 liters, in which the bottom must be sandy , since fiddler crabs have a habit of burrowing in the sand to hide and protect themselves.
It is a species not very sensitive to variations in salinity and pH . The ideal temperature is between 24º and 26ºC, and the pH can be between 7 and 8.9.
It is usual for it to come out of the water looking for humid and well-lit areas, which must be provided, either with rocks (which can also serve as protection) or some woods.
If the chosen aquarium is only to have crabs, mixed with some other variety of invertebrates ,It should not be completely filled, so that we leave the habitat most similar to the original: coast or beach.
Plants can be added to the aquarium, but it is recommended that they be made of plastic, because it would break them.

Aquarium decoration

  • Best aquarium sand
  • Best gravel for aquarium
  • Best akadama for aquarium
  • Best Aquarium Ornaments 
  • Best logs for aquariums
  • Best rocks for aquariums
  • Best backgrounds for aquariums
  • Best artificial plants


The Uca tangeri is omnivorous, it will eat both live or dead prey of animal origin. In the aquarium we can offer them brine shrimp, plankton and fish scales.
They will also feed on algae, both of which we can provide them, and those that may appear naturally in the aquarium.
Crabs tend to change their exoskeleton (their skin) constantly in order to grow, we do not have to help them to change it, nor should we worry about them eating less or stopping eating in that period.
Nor should you remove the skin, since it is common for them to eat it, due to the calcium it contains.

Everything you need to maintain your aquarium

  • Best digital pH meter
  • Best Aquarium Test
  • Best anti-algae
  • Best bacteria for aquarium
  • Best siphoner for aquarium
  • Best Aquarium Water Clarifiers
  • Best reverse osmosis filters for aquarium
  • Best UV lamps for aquariums

Behavior and compatibility

The fiddler crab is not aggressive towards other species, although the males do show territorial , so if we have several in the aquarium, they must have enough space.
Due to the specific needs of the aquarium, they can share space with other crustaceans and with some mollusks.


They are not an easy species to reproduce in the aquarium. It is known that in the natural state, procreation begins with courtship by the male, who attracts the female to his cave or burrow.
The female carries the eggs fertilized by the male for about two weeks, during which she remains hidden in the cave.
After that period of time, the female leaves the cave when the eggs are about to hatch.
The larvae of the fiddler crab live in the sea, until they complete their metamorphosis.


The fiddler crab is a resistant species, which is not usually attacked by diseases, but problems can arise if we do not keep the water in the right conditions of temperature and cleanliness.
We should not be scared when we see that they change their skin, nor if we observe that they have lost any of their limbs, they regenerate.
It is convenient to make periodic changes of the water, we will notice that they become more active.

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