Watermelon fiddler crab

Care at a glance

Overview

Keep a group with more females than males on the beach of a brackish paludarium, where they dig, wave, and sort sand all day at ground level. Males spar but rarely hurt each other, and they ignore anything they cannot catch, which is nearly everything. They pick algae and detritus out of the sand, so feed sinking pellets, algae wafers, blanched vegetables, and a little frozen food on the beach or at the water's edge, plus cuttlebone for calcium. Brackish snails are safe company; fish are a poor match for a setup that is mostly sand.

In the wild

The watermelon fiddler crab lives on the muddy sand of mangrove edges, lagoons, and river mouths across the western Pacific, from Taiwan and the southern islands of Japan down through the Philippines and Indonesia to eastern Australia and the Pacific islands. Like every fiddler it spends most of its time out of the water, so it needs a paludarium with a deep sand beach, a shallow pool, and a tight lid. It is sold as a freshwater crab and lasts a while in fresh water, but it is a brackish animal, so mix marine salt to a specific gravity of 1.005 to 1.015. Keep it warm at 24 to 29 C with a pH of 7.8 to 8.4, and give a small group a footprint of 40 liters or more.

Good to know

This is Paraleptuca crassipes in the family Ocypodidae, described by White in 1847 as Gelasimus crassipes and known in the trade as Uca crassipes until the 2016 revision. The carapace is usually about 2.5 cm across, with the largest crabs a little over 3 cm. The colors that earned the trade name are a crimson red carapace with black patches, a pink red claw on the male, and sky blue patches on the face and around the leg bases. It changes shade with the tide, darker by day and paler at night. The larvae develop in the sea, so it does not breed in captivity.

Common questions

Related species

• 

  Atlantic sand fiddler crab

  Leptuca pugilator

  1 in (2.5 cm) · 11 gal (40 L)

  1 in (2.5 cm)11 gal (40 L)68–82°F (20–28°C)

• 

  Fiddler crab

  Minuca minax

  1.6 in (4 cm) · 10 gal (38 L)

  1.6 in (4 cm)10 gal (38 L)75–82°F (24–28°C)
• Batik crab

  Metasesarma obesum

  1 in (2.5 cm) · 11 gal (40 L)

  1 in (2.5 cm)11 gal (40 L)72–82°F (22–28°C)

• 

  Brackish hermit crab

  Clibanarius longitarsus

  2 in (5 cm) · 16 gal (60 L)

  2 in (5 cm)16 gal (60 L)75–84°F (24–29°C)

• 

  Red claw crab

  Parasesarma bidens

  2 in (5 cm) · 10 gal (38 L)

  2 in (5 cm)10 gal (38 L)72–82°F (22–28°C)

• 

  African mangrove crab

  Goniopsis pelii

  2.4 in (6 cm) · 24 gal (90 L)

  2.4 in (6 cm)24 gal (90 L)75–86°F (24–30°C)