Description

Blue Knuckle Hermit Crab (Calcinus elegans)
The Electric Blue Hermit Crab is a vibrant and eye-catching species, easily identified by its bright blue legs with black banding. Larger and more robust than many dwarf hermits, this crab is an active scavenger that consumes algae, detritus, and leftover food. While reef-safe, it can be more aggressive than smaller hermits and may compete with snails for shells or disturb unsecured frags. Best kept in tanks with plenty of extra shells and secure rockwork to accommodate its size and activity.

  • Care Level: Easy to Moderate

  • Reef Safe: With caution (may harass snails or move frags if underfed)

  • Diet: Algae, detritus, leftover food

  • Behavior: Active scavenger; more assertive than dwarf hermits

  • Recommended Tank Size: 30+ gallons

🦀 Blue knuckle Hermit Crab (Atlantic)

Scientific Name:  Calcinus elegans
Common Name: Blue Knuckle Hermit Crab
Size: ~0.5 to 1.5 inch
Reef Safe: ✅ Yes
Temperament: Generally peaceful, mildly competitive over shells
Diet: Omnivorous – eats film algae, detritus, leftover food, cyanobacteria
Tank Role: Algae grazer and substrate cleaner

Blue Knuckle Hermit Crab - Calcinus elegans

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      DescriptionDescription

      🔍 Description:
      The Blue Leg Reef Hermit Crab is a small but mighty clean-up crew member, instantly recognizable by its bright blue legs with dark banding. Found in the warm waters of the Caribbean and western Atlantic, it plays a vital role in reef aquariums by consuming nuisance algae and detritus from hard-to-reach crevices and sand beds.

      Though mostly peaceful, these hermits can become competitive if not provided with extra shells, occasionally targeting snails or other hermits for a better home. Despite their size, they’re tough, active, and effective algae grazers.

      Must HaveMust Have

      ✅ Why They’re a Must-Have:

      Excellent Algae Cleaner: Feeds on film algae, hair algae, and even some cyanobacteria

      Compact & Versatile: Great for nano tanks or large reef systems alike

      Sandbed Stirrer: Helps prevent detritus buildup in substrate

      Colorful & Active: Always moving and visibly working

      Notes for SuccessNotes for Success

      ⚠️ Notes for Success:

      Offer Plenty of Spare Shells: Reduces aggression toward snails and other hermits

      Use in Moderation: Too many can overwhelm peaceful tankmates or outcompete others

      Supplement in Clean Tanks: Provide small amounts of algae-based pellets or flakes

      May Tip Over Frags: Active behavior can occasionally knock loose coral plugs

      Best Used ForBest Used For

      🧽 Best Used For:

      Reef tanks battling light algae issues

      Nano reefs and mixed reef systems

      Aquarists looking for small, hardy grazers with visual appeal

      Description

      Blue Knuckle Hermit Crab (Calcinus elegans)
      The Electric Blue Hermit Crab is a vibrant and eye-catching species, easily identified by its bright blue legs with black banding. Larger and more robust than many dwarf hermits, this crab is an active scavenger that consumes algae, detritus, and leftover food. While reef-safe, it can be more aggressive than smaller hermits and may compete with snails for shells or disturb unsecured frags. Best kept in tanks with plenty of extra shells and secure rockwork to accommodate its size and activity.

      • Care Level: Easy to Moderate

      • Reef Safe: With caution (may harass snails or move frags if underfed)

      • Diet: Algae, detritus, leftover food

      • Behavior: Active scavenger; more assertive than dwarf hermits

      • Recommended Tank Size: 30+ gallons

      🦀 Blue knuckle Hermit Crab (Atlantic)

      Scientific Name:  Calcinus elegans
      Common Name: Blue Knuckle Hermit Crab
      Size: ~0.5 to 1.5 inch
      Reef Safe: ✅ Yes
      Temperament: Generally peaceful, mildly competitive over shells
      Diet: Omnivorous – eats film algae, detritus, leftover food, cyanobacteria
      Tank Role: Algae grazer and substrate cleaner

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