Red Giant Hermit Crab

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The Red Giant Hermit Crab (Dardanus megistos) is a large, eye-catching marine crustacean recognised by its reddish-orange legs, bright white spots and bristly appearance. It lives inside an empty gastropod shell, which protects its soft abdomen, and may change shells as it grows.

This species is an active scavenger and opportunistic omnivore. It consumes leftover food, carrion and other organic material, but its size and feeding behaviour mean it is not a safe choice for most reef aquariums. It may prey on snails, smaller crabs and other invertebrates, disturb corals or rockwork, and move unsecured decorations while searching for food.

Red Giant Hermit Crabs are best suited to a spacious, established marine aquarium with sturdy rockwork and plenty of appropriately sized spare shells. Provide a varied diet of marine meaty foods and monitor feeding to prevent waste build-up.

Quick Care Guide

• Scientific Name: Dardanus megistos

• Common Name: Red Giant Hermit Crab / Giant Red Hairy Hermit Crab / White-spotted Hermit Crab

• Family: Diogenidae

• Type: Marine Invertebrate — Hermit Crab

• Adult Size: Body length can reach approximately 20 cm; overall size varies with its shell.

   

• Temperament: Aggressive and opportunistic

• Care Level: Moderate

• Minimum Aquarium: 300 L+; a much larger system is preferable for a large adult

• Temperature: 24–27°C

• pH: 8.1–8.4

• Salinity: 1.023–1.026 SG

• Diet: Omnivore / Scavenger

• Food: Chopped shrimp, mussel, squid, marine pellets and suitable algae foods

• Tank Level: Substrate and rockwork

• Reef Safe: No

• Suitable For: Large, established fish-only marine aquariums

• Aquascape: Secure rockwork, open substrate and hiding places

• Special Requirement: A selection of empty shells in progressively larger sizes

• Copper Sensitivity: High

Frequently Asked Questions

Is the Red Giant Hermit Crab reef safe?

No. It can prey on snails, worms and other invertebrates, disturb corals and move unsecured rockwork. It is best kept in a large fish-only aquarium.

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How big does it grow?

Its body can reach around 20 cm, although size varies. Remember to allow for the shell, which adds to the crab's overall bulk. 

What does it eat?

It scavenges leftover food and detritus, but should also receive meaty foods such as chopped shrimp, mussel and squid, alongside suitable prepared foods.

Does it need spare shells?

Yes. Provide several empty gastropod shells of different sizes. As the crab grows, it needs larger shells for protection.

Can I keep it with other hermit crabs?

This is risky. It may attack smaller hermit crabs or compete aggressively for shells. Keeping a single specimen is generally the safer option.

Can it live with marine fish?

It is best housed with larger, robust fish that are unlikely to be eaten. Small, slow-moving or bottom-dwelling fish may be vulnerable, especially at night.

Common Mistakes

• Keeping it in a reef aquarium with valuable corals and invertebrates.

• Underestimating its adult size and strength.

• Failing to provide larger replacement shells.

• Leaving rockwork unsecured where it can be knocked over.

• Assuming it can live entirely on leftover food.

• Housing it with small fish, snails or ornamental shrimp.