Electric Blue Hermit Crab

Care at a glance

Overview

An active scavenger that grazes green hair algae and cyanobacteria and cleans up detritus and leftover food, making it a genuinely useful cleanup-crew animal. It is generally peaceful toward fish and corals, so it counts as reef-safe, but it is not snail-safe: if it outgrows its current shell and no spares are available, it will attack and kill a snail to take its shell. Keep a good supply of empty shells in a range of sizes, and expect some squabbling over shells if several are kept together in a small tank.

In the wild

Ranges across the Indo-Pacific from East Africa to Hawaii and French Polynesia, north to southern Japan and south to northern Australia, living intertidally and on shallow coral reef and rubble down to about 5 metres. It grazes rock and rubble for algae and organic debris, carrying its shell home wherever it forages. In the aquarium it wants live rock with algae growth to pick at and enough open rock and sand to move around freely.

Good to know

Calcinus elegans is a hermit crab in the family Diogenidae, unmistakable for its electric blue legs banded in black and yellow, blue eyestalks, and green claws tipped in white. Adults reach about 5 cm in body length and grow into shells up to 7.5 cm long. Like other Calcinus it is a left-handed hermit: its left claw is enlarged and works as a door that seals the shell opening when it withdraws inside.

Did you know

Its enlarged left claw works as both a weapon and a trapdoor, folding flush across the shell opening to seal the crab safely inside whenever a predator gets too close.

Related species

• 

  Scarlet Zebra Hermit Crab

  Calcinus laevimanus

  1.2 in (3 cm)20 gal (75 L)72–79°F (22–26°C)

• 

  Halloween Hermit Crab

  Ciliopagurus strigatus

  2 in (5 cm)20 gal (75 L)72–79°F (22–26°C)

• 

  Scarlet Reef Hermit Crab

  Paguristes cadenati

  1.6 in (4 cm)11 gal (40 L)72–79°F (22–26°C)

• 

  Blue-Leg Hermit Crab

  Clibanarius tricolor

  1 in (2.5 cm)11 gal (40 L)72–79°F (22–26°C)
• Mexican Red-Leg Hermit Crab

  Clibanarius digueti

  1 in (2.5 cm)11 gal (40 L)72–81°F (22–27°C)

• 

  Porcelain Anemone Crab

  Neopetrolisthes maculatus

  3 in (7.5 cm)11 gal (40 L)72–79°F (22–26°C)