Orange Fiddler Crab

The Orange Fiddler Crab refers to vividly orange-coloured fiddler crab species traded under this common name, most commonly Gelasimus borealis or allied species from Indo-Pacific tidal mudflats and sandy shores. Males display the characteristically enormous asymmetric major claw — the 'fiddle' — in vivid orange or red-orange, which is waved in elaborate courtship and territorial displays.

In captivity, orange fiddler crabs require the standard fiddler crab paludarium setup: a sandy or muddy substrate sloping from a brackish water zone up to a dry above-waterline burrowing area. Each male requires territory around its burrow entrance, and groups with multiple males produce continuous display behaviour that is highly entertaining. Females and sub-adults bear two equal smaller claws.

Diet is based on fine organic particles processed by the smaller feeding claw from the substrate. In captivity this is supplemented with algae powder, fine sinking pellets, powdered dried shrimp, and organic-rich sand. These crabs are sensitive to water quality changes and do not tolerate copper-based medications. Breeding larvae are planktonic and require marine conditions.

Water: 22–30°C, pH 7.5–8.5, GH 10–22, KH 4–14; brackish 1.005–1.015 SG; sandy slope tidal shoreline required. Tank: minimum 60 L paludarium; sandy burrowing substrate above waterline; brackish water zone; mangrove decor; secure lid. Feeding: detritivore/omnivore — algae powder, fine sinking pellets, powdered dried shrimp, organic-enriched sand. Breeding: planktonic marine larvae; captive breeding through larval stage not practical. Compatibility: social groups with mixed sexes; males territorial over burrows; do not mix with fish that nip appendages.