Description

The Anemone Hermit Crab (Dardanus pedunculatus) is a visually fascinating and moderately hardy creature in the aquarium trade, but it is not considered safe for most reef tanks.

Its large size and natural predatory/scavenging behaviours make it a risk to corals and other small invertebrates.

Reef Compatibility: Not Reef Safe
The most critical factor in keeping this crab is its safety profile:

Risk to Corals: High. Dardanus species are large and opportunistic carnivores/scavengers. They are known to knock over and potentially damage or consume small corals, polyps, or sessile invertebrates while foraging or moving their large shell.

Risk to Invertebrates: High. They are known to prey upon small invertebrates, including snails and other smaller hermit crabs, often killing them to obtain a new shell or simply for a meal.

Best Placement: This species is best suited for a Fish-Only (FO) or a Fish-Only-With-Live-Rock (FOWLR) system, rather than a mixed reef.

General Care and Behaviour
Care Level: Easy/Beginner. They are generally hardy and easy to feed.

Max Size: Up to 3-4 inches (excluding the shell), making them a large hermit crab.

Minimum Tank Size: Due to their size and need for space, a tank of 55 gallons or more is often recommended.

Diet: Carnivore/Scavenger. They require meaty foods and will scavenge for detritus, dead organisms, and algae. They must be actively fed; supplemental foods should include pieces of raw table shrimp, frozen mysis/krill, or high-quality sinking pellets.

Temperament: Semi-Aggressive/Opportunistic. They are generally peaceful toward large, healthy fish, but will seize any opportunity to grab food or a new shell.

The Symbiotic Relationship
The unique feature of Dardanus pedunculatus is its symbiotic relationship:

The Anemone: The crab actively collects certain types of sea anemones (often Calliactis or Verrillactis species) and places them on its shell. The crab taps the anemone until it loosens its grip, then transfers it.

Mutual Benefit: The anemones benefit by being moved to new feeding locations and scavenging morsels from the crabs messy eating. The crab is protected from predators (like octopuses) by the anemones’ stinging tentacles.

Shell Upgrades: When the crab grows and needs a new, larger shell, it will carefully transfer its resident anemones to the new shell.

In summary: While they are beautiful and fascinating to watch, the Anemone Hermit Crab is a poor choice for a delicate coral reef tank but a great, charismatic addition to a larger, fish-focused system.

Would you like some recommendations for a reef-safe hermit crab that stays small and is known for great algae control?