Electric Blue Hermit Crab

The Electric Blue Hermit Crab (Calcinus elegans), also sold as the Electric Blue Leg Hermit or Elegant Hermit Crab, is one of the most striking hermits in the reef hobby. It is beloved for its black legs banded in vivid electric blue and its bright orange antennae, a combination that stands out against rockwork and sand.

Native to reefs across the tropical Indo-Pacific, this hermit grows larger than common blue leg and red leg hermits. It earns its place in the cleanup crew by grazing nuisance algae and scavenging uneaten food, while adding far more color than a typical cleanup crab.

Quick Care Guide

Care Level: Easy
Minimum Tank Size: 20 gallons
Temperament: Peaceful to Semi-Aggressive
Diet: Omnivore
Reef Safe: Yes, with caution
Adult Size: About 1–1.5 inches
Region: Indo-Pacific
Scientific Name: Calcinus elegans

Tank Requirements

Provide an established aquarium with plenty of live rock to climb and graze, plus open sand to scavenge. Keep several empty shells on hand, each slightly larger than the crab’s current home, so it can move up in size as it grows.

Because of its larger size, this hermit may occasionally topple small or unsecured coral frags. Glue frags in place before adding it.

Diet and Feeding

Electric Blue Hermits are omnivorous. They pick at film algae, hair algae, and detritus, and quickly find leftover meaty foods on the sand or rockwork. When algae runs low, supplement with dried seaweed, algae wafers, or sinking pellets two to three times per week.

Temperament and Tankmates

These hermits are generally peaceful with fish and corals. Without enough empty shells, they may attack snails to take over their shells, so providing spare shells is the best way to protect your snail population.

Avoid triggerfish, puffers, hawkfish, and large wrasses, which may prey on hermit crabs.

Reef Compatibility

The Electric Blue Hermit Crab is reef safe with caution. It does not eat corals, but its size and activity can dislodge loose frags, and it may compete with snails for shells.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Acclimate slowly and keep parameters stable to support healthy molting. Invertebrates are highly sensitive to copper, and copper-treated water or medications should never be added to an aquarium that houses them.

Common Considerations

• Provide spare shells: Offer three to five empty shells per crab in sizes slightly larger than its current shell.

• Protect your snails: Hermits without spare shells may kill snails for theirs.

• Secure frags: Larger hermits can knock over unattached corals.

• Molting is normal: A hermit may bury itself or hide for a few days while molting.