Electric blue hermit crab (Calcinus elegans) care guide

Group
Other invertebrates
Other names
Blue line hermit crab, Elegant hermit crab, Pagurus elegans
Family
Diogenidae
Origin
Indo-West Pacific from East Africa to Hawaii and Japan; shallow reefs to about 20 m
Water
saltwater
Temperature
22–27°C
pH
8.1–8.4
Hardness
dKH 8–12, SG 1.023–1.025
Care level
beginner
Temperament
semi_aggressive
Reef safe
with_caution

Care

The electric blue hermit crab is one of the most striking reef hermits: its legs have alternating bright blue and black bands, its claws are olive-green with white-speckled tips, and it has bright blue eyes and orange antennae. Hawaiian animals may have orange rather than blue leg bands. It is the only Calcinus covered in fine hairs. Our sources do not give a size; it is a small-to-medium hermit of a few centimetres. In the wild it lives in shallow, clear tropical water, in tidal and subtidal zones down to about 20 m, at roughly 20–30 °C and normal sea-water salinity, foraging at night for detritus and decaying plant and animal matter. Standard reef conditions suit it in the aquarium. It is a good clean-up crew scavenger, eating detritus, leftover food and some algae. Hermit crabs choose and change shells as they grow, and this one is choosy about shell weight, stability and size. Always provide a few spare empty shells a little larger than the one it wears; without them hermits may kill snails to take their shells. One or two in a typical reef tank is usually enough, as they can squabble with each other over shells. Copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most invertebrates. Sources: Wikipedia (en.wikipedia.org/wiki/Calcinuselegans). Checked October 2026.

Diet

A nocturnal omnivore and detritivore. Eats detritus, leftover fish food, decaying plant and animal matter and some film and hair algae. Feed small amounts of pellets, frozen foods and dried seaweed if the tank is very clean.

Breeding

Before mating the male turns the female's shell and strokes his claws around its opening; unlike most crustaceans the pair do not leave their shells to mate. Females carry eggs that hatch into planktonic larvae, which are not raised in home aquaria.

Compatibility and tank mates

Generally reef safe but treat with caution: it may pick at corals or clams when hungry, knock over frags and kill snails for their shells if spare shells are lacking. Fights over shells with other hermits. Avoid predatory fish such as triggers, puffers and large wrasses.

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

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