30 Fiddler Crab Quick Facts

1.  Fiddler crabs are brackish and marine water animals.

2.  They need land sand/mud and water to survive.

3.  Fiddlers are arthropods just like insects, isopods, bugs, spiders and other arachnids.

4.  They are crustaceans with 8 legs and 2 claws.  Females have two small feeder claws.  Males have one large claw and one small feeder claw.

5.  Fiddlers have gills that must remain moist for them to be able to breathe.

6.  Just like other arthropods, fiddlers have an exoskeleton aka shell.

7.  To grow in size or to regrow a lost limb, fiddlers molt their exoskeleton aka shell.

8.  It is possible for fiddlers to live up to 7 years or longer.

9.  Male fiddlers wave their large claw in a special dance to attract females.

10.  Females choose the males based on the male's waving and claw size.

11.  Female fiddlers dig burrows to lay their eggs in.  Some species keep their eggs attached to their bodies and release them during a high tide.  Some eat the eggs off of themselves if they cannot release them at high tide.

12.  Baby fiddlers are called larvae.

13.  Baby fiddlers are part of the zooplankton during their larval stage.

14.  Larval baby fiddlers eat phytoplankton and rotifers.

15.  It is difficult to get baby fiddlers to survive in an aquarium due to the filter, predation by other aquarium animals (including the parent crabs), lack of proper deep ocean conditions, and lack of proper food.

16.  Fiddlers treat their known neighbor crabs differently than they treat unfamiliar crabs.

17.  Male fiddlers do a defensive and territorial waving pattern with their claws when danger or other crabs come near their personal space.

18.  Adult fiddlers in captivity can eat fresh and freeze dried shrimps, plankton, algae, seaweed, bloodworms, fish flakes, fish pieces, and even dead insects.

19.  Many fiddlers enjoy burrowing in sand and/or mud, particularly the females but males will burrow too.

20.  Water temperatures between 75 degrees Fahrenheit and 85 degrees Fahrenheit are ideal for adult fiddler crab aquariums. 

21.  Four fiddlers can live together in a 10 gallon tank.  3 females and 1 male.

22.  Male fiddlers fight each other over territory.  Sometimes the fighting gets violent and one fiddler may lose a limb or an eye-stalk (the vision part of the eye stalks are not likely to regrow).

23.  Fiddlers become lighter in color at night.

24.  Some fiddlers in captivity can acquire an algae growth.  If this happens, reduce the amount of time the light is on the aquarium.  The algae should not hurt the crab unless it grows on the gills, mouth parts, or eyes or becomes so large it hinders feeding.

25.  As the crabs age, they molt less frequently, eventually getting to a point where they no longer molt at all unless a limb is lost.  During youth the crabs molt very often.  During early adulthood, molting every 8 weeks or so is normal.

26.  It is possible for fiddlers to become depressed living in a tank setting.  Signs of fiddler depression include: not waving anymore (males only), nearly constant seclusion in a burrow, aquarium ornament or under something, no longer eating, constant attempts to escape (this could be a sign of bad water conditions).

27.  Fiddler depression can be caused by tank changes, stress, general unhappiness due to having once lived in the ocean but now having to live in captivity, lack of mates, inadequate water salinity (either too high or too low), ammonia in the water, chlorine/chloramine or other harmful substance/chemical in the water, lack of tides, temperature changes or inadequate temperature (too high or too low), inadequate water depth (too high or too low), territorial disputes with tank mates (sometimes a group or an individual crab will restrict the movements of another), etc.

28.  Some crabs exhibit winter behavior.  Some will burrow when the temperature gets lower and not come out for long periods of time, if at all, until the temperature of the water/land gets higher.  Many crabs instinctively know when it is winter time and will burrow, become sluggish, eat a bit less, or spend their time mostly in the water.  Those are normal behaviors for winter and lower tank temperatures.

29.  Fiddlers are capable of producing memories, communication, deceptive communication, and other social behaviors you may not expect.

30.  Many fiddlers eat in the morning, between the hours of 4am and 10am, scavenging the sand and the water for food debris.  As afternoon approaches, crabs may go into hiding.