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Fiddler Crab
Uca pugnax
Animalia›Arthropoda›Malacostraca›Decapoda›Ocypodidae
Fiddler crabs are iconic semi-aquatic crabs known for their distinctive oversized claw used in territorial displays and courtship. They require a specialized setup with both land and water areas, making them moderately challenging but rewarding pets. These social crabs are best kept in small groups and display fascinating burrowing and feeding behaviors.
At a glance
- Size
- 2 in
- 5 cm
- Min tank
- 20 gal
- 76 L
- Group
- 3+
- Temp
- 68–79°F
- 20–26°C
- pH
- 7.0-8.0
- GH
- 143–268 ppm
- 8–15 dGH
- Temperament
- Semi-aggressive
- Swims
- Bottom
- Lifespan
- 2-3 yrs
Ammonia 0 ppm and nitrate under 20 ppm.
Care
Diet
Fiddler crabs are detritivores that scavenge the substrate for organic matter, biofilm, and algae. Supplement with blanched vegetables (zucchini, spinach), algae wafers, and occasional protein sources like small pieces of shrimp or fish food. Feed small amounts 2-3 times weekly.
Behavior
Fiddler crabs are highly social and display complex territorial and courtship behaviors, including the characteristic waving of their oversized claw. They are primarily nocturnal and spend much of their time burrowing in sand or mud, creating elaborate tunnel systems. They require access to both shallow water and dry land areas to thrive.
Breeding
Breeding in captivity is extremely difficult and rarely successful in home aquariums. Females produce larvae that require brackish to marine conditions to develop, making freshwater breeding impossible. Most captive fiddler crabs are wild-caught, and breeding is best left to specialized facilities.
Tank mates
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Common diseases 4Shell Erosion / Exoskeleton Damage, Molting Complications, Parasitic Infections (Copepods, Isopods), Bacterial Infection / Septicemia
Shell Erosion / Exoskeleton Damage
Pitting, discoloration, or softening of the exoskeleton; missing limbs or claws
Ensure proper water parameters (pH 7.0-8.0, adequate calcium), provide hiding places to reduce stress and aggression, perform regular water changes
Molting Complications
Inability to shed exoskeleton, lethargy, loss of appetite, death during molt
Maintain stable water conditions and temperature; provide adequate humidity in land area; ensure low stress environment; do not disturb molting crabs
Parasitic Infections (Copepods, Isopods)
Visible parasites on body, lethargy, loss of appetite, abnormal behavior
Quarantine affected crab; perform frequent water changes; use brackish water dips if available; consult specialized aquatic veterinarian
Bacterial Infection / Septicemia
Discoloration, soft spots on exoskeleton, lethargy, refusal to eat
Improve water quality immediately; increase water changes; maintain optimal temperature; provide stress-free environment with adequate hiding; antibiotics rarely effective in invertebrates
Legality
No state or federal restrictions on record.
Not legal advice, and possibly incomplete or out of date. Rules vary by state and change over time; check with your state wildlife or agriculture agency before buying, keeping or shipping it.
The care information here is written with AI help, so it can contain mistakes. Spot one? Tell us and we'll fix it.
At a glance
- Size
- 2 in5 cm
- Min tank
- 20 gal76 L
- Group
- 3+
- Temp
- 68–79°F20–26°C
- pH
- 7.0-8.0
- GH
- 143–268 ppm8–15 dGH
- Temperament
- Semi-aggressive
- Swims
- Bottom
- Lifespan
- 2-3 yrs
Ammonia 0 ppm and nitrate under 20 ppm.
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