Atlantic sand fiddler crab (Leptuca pugilator) care guide

Group
Other invertebrates
Other names
Uca pugilator, Sand fiddler crab, Fiddler crab, Calico fiddler crab
Family
Ocypodidae
Origin
Atlantic coast of North America and the Gulf of Mexico, Massachusetts to Florida and Texas; estuaries and sheltered sandy or muddy shores
Water
brackish
Maximum size
2.5 cm
Temperature
20–28°C
pH
7.8–8.4
Hardness
SG 1.005–1.015 (brackish)
Minimum tank
75 litres
Care level
intermediate
Temperament
semi_aggressive

Care

The Atlantic sand fiddler crab is a small crab of tidal mud-flats and sheltered sandy shores on the east coast of North America. The carapace is square and about 2–2.5 cm wide. Males have one hugely enlarged claw, up to about 3.5–4 cm long, which they wave to attract females and use to fight rival males; if it is lost, a new claw grows and the other side may become the large one. It was formerly called Uca pugilator and was moved to the genus Leptuca in 2016. Not a freshwater crab: fiddler crabs are often sold as freshwater animals, but they live in estuaries and need brackish water and, above all, dry land. They spend most of their time out of the water. Tank set-up: a semi-terrestrial set-up (a paludarium or 'beach' tank) of 75 litres or more with a large land area of damp sand or sand-mud mix deep enough to dig burrows, and a shallow brackish pool. Keep a secure lid and warm, humid air. They can live in huge colonies in the wild, so a small group with more females than males works best; males spar with their big claws. Water: brackish, around specific gravity 1.005–1.015, at about 20–28 °C. Use marine salt, not table salt. Our sources cover its biology but not its aquarium care; the figures are general guidance, not from a source. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most invertebrates. Never dose them in a tank holding this animal, check the label of any treatment or fertiliser, and use a separate hospital tank for fish. Sources: Wikipedia (en.wikipedia.org/wiki/Leptucapugilator). Checked October 2026.

Diet

A deposit feeder: it scoops sand and mud and sifts out algae, bacteria and detritus with its small claw (males feed with the small claw only). Offer sinking pellets, flake, algae wafers and small frozen foods scattered on damp sand.

Breeding

Males wave their large claw to attract females into their burrows. Females carry eggs under the abdomen and release the larvae into the sea at high tide; the larvae need full-strength sea water and plankton foods. Breeding in home tanks is very rarely successful.

Compatibility and tank mates

Best kept in its own beach tank. Males fight each other. Fish in the pool may nip them, and they may catch small or slow tankmates. Not suited to normal freshwater or fully marine tanks.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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