TankBud

Anemone hermit crab

Dardanus pedunculatus

Also known as Hermit crab with anemone

SaltwaterCrab

Anemone hermit crab (Dardanus pedunculatus)
Nhobgood Nick Hobgood · CC BY-SA 3.0

Care at a glance

Temperature
72–81°F
22–27°C
pH
8.1–8.4
Adult size
3.9 in
10 cm
Minimum tank
40 gal
150 L
Temperament
Aggressive
Social behavior
Solitary
Own kind
One per tank
Tankmates
With caution
Swim level
Bottom
Diet
Carnivore
Difficulty
Easy
Breeding
No record
Rarity
Common
Reef safe
Not reef safe
Family
Diogenidae
Origin
Indo-Pacific, from East Africa and the Seychelles to Japan and Hawaii

Overview

The anemone hermit crab is an aggressive, active scavenger for a rough fish-only or large predator tank. It is easy to keep.

Did you know

Anemone hermit crabs starved by Imafuku and colleagues in a 2000 study at Shirahama, Japan, pulled their own anemones off the shell and ate them. Crabs kept in pairs also stripped anemones off their partner's shell. A well-fed crab protects its anemones, but a hungry one turns them into emergency rations.

Caring for the anemone hermit crab

Give the anemone hermit crab a tank of at least 40 gal (150 L) with a sand bed and dim light. Build stable rockwork it cannot topple, since it knocks over frags and loose rock. Keep a supply of large empty shells on hand, such as whelk and turban shells.

Keep the water at 72 to 81°F (22 to 27°C) and a pH of 8.1 to 8.4, with a specific gravity of 1.023 to 1.025. Feed it meaty foods such as raw shrimp, clam, mussel, squid and silversides two or three times a week. The anemones need their own feeding of meaty bits to stay on the shell.

It eats snails, small hermit crabs, tube worms and any fish it can catch asleep on the sand. Its anemones sting whatever they touch, so it is not reef safe. Medium to large fish that stay off the bottom are fine company. Keep one per tank, since two will steal each other's anemones and fight over shells.

Good to know

Dardanus pedunculatus is a left-handed hermit crab in the family Diogenidae. Herbst described it in 1804 as Cancer pedunculatus. It has a mottled tan and cream carapace and white eyestalks banded in red. Its left claw is much larger than the right, and it uses that claw to seal the shell opening. Its trademark is the anemones it collects at night. It strokes and taps a Calliactis polypus until the anemone lets go of the rock, then sets it on its own shell. When it moves to a bigger shell, it moves the anemones too. The stinging tentacles put off octopus, its main predator, and the anemones get a ride and scraps from the crab's messy meals.

In the wild

The anemone hermit crab lives on coral reefs, reef flats and sandy lagoons across the Indo-Pacific. It ranges from East Africa and the Seychelles to Japan and Hawaii, from the intertidal down to about 95 m. It is a big, heavy hermit that drags a large snail shell, usually with one or more Calliactis anemones stuck to it.

Common questions

What size tank does an anemone hermit crab need?

An anemone hermit crab needs at least 40 gal (150 L). It spends most of its time in the bottom.

What temperature and pH does an anemone hermit crab need?

An anemone hermit crab is comfortable at 72–81°F (22–27°C) with a pH of 8.1–8.4.

What does an anemone hermit crab eat?

An anemone hermit crab eats meaty foods such as raw shrimp, clam, mussel, squid and silversides, two or three times a week. Its anemones need their own meaty bits to stay on the shell.

How big does an anemone hermit crab get?

An adult anemone hermit crab reaches about 3.9 in (10 cm).

Related species