Why is my Scarlet Hermit Crab out of its shell?

Hermit crabs usually leave their shells for two reasons: they are actively moulting, or they are searching for a larger shell. Ensure you have provided several empty shells of various sizes. If moulting, the crab will hide in a crevice until its new exoskeleton hardens.

Will the Scarlet Reef Hermit eat my corals?

No, they are considered completely reef safe. They will carefully walk over corals to pick off algae and detritus but will not consume or harm the coral tissue itself.

Do I need to feed my hermit crabs?

In an established tank with algae and leftover fish food, they will scavenge enough to survive. However, in pristine or very new tanks, you should drop in sinking algae wafers or small pieces of marine meat to ensure they do not starve.

Will they kill my snails for their shells?

Scarlet Reef Hermits are one of the least likely species to kill snails for shells, but it can still happen if they are desperate. The best way to prevent this is to maintain a large collection of empty shells on the sand bed.

Are they sensitive to water changes?

While hardy, they are sensitive to sudden swings in salinity and temperature, as well as high nitrates. Furthermore, they are highly intolerant of copper; never use copper-based fish medications in a tank with hermit crabs.

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Scarlet Reef Hermit

Paguristes cadenati

The Scarlet Reef Hermit Crab is a vibrant, hard-working member of the marine cleanup crew, prized for its bright red legs and peaceful nature.

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Ideal Conditions

Temperature: 23 – 28 °C
pH range: 8.1 – 8.4
Hardness: 8 – 12 dGH
Salinity: 1.023 – 1.025 SG
Adult size: 3 – 4 cm
Nano tank: 20 litres+
Lifespan: 1 – 2 years
Diet: omnivore
Water flow: moderate
Preferred setup: Live rock, sand bed, and a supply of empty shells.

About the Scarlet Reef Hermit

Native to the Western Atlantic and Caribbean Sea, the Scarlet Reef Hermit (*Paguristes cadenati*) is one of the most popular invertebrates in the marine aquarium hobby. Unlike many other hermit crabs, they are overwhelmingly peaceful and heavily focused on consuming nuisance algae and detritus. Their striking scarlet legs and bright yellow eyestalks make them highly visible and attractive additions to the bottom of the tank. Because they rely on scavenged gastropod shells for protection, their appearance is constantly changing as they grow and upgrade their homes.

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Is it right for your tank?

Check Scarlet Reef Hermit against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Scarlet Reef Hermit comes from

Native range

Caribbean Sea, Western Atlantic Ocean, Gulf of Mexico

Countries / regions

Bahamas, Mexico, United States

Habitat

Coral reefs, rocky rubble zones, and seagrass beds.

Widely distributed throughout the Caribbean reef systems.

Similar species

Blue Leg Hermit Crab
Clibanarius tricolor
Halloween Hermit Crab
Ciliopagurus strigatus
Zebra Hermit Crab
Calcinus laevimanus

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Ocellaris Clownfish
Amphiprion ocellaris
Peaceful fish that occupy the water column and will completely ignore bottom-dwelling hermit crabs.
Great
Skunk Cleaner Shrimp
Lysmata amboinensis
Another peaceful invertebrate; they occupy different ecological niches and will coexist harmoniously.
Great
Trochus Snails
Trochus spp.
Scarlet Hermits are generally peaceful towards snails, provided ample empty shells are available for the hermit's growth.
Great
Dwarf Blue Leg Hermit Crab
Clibanarius tricolor
Both compete for the same food sources and potential shells, which can occasionally lead to squabbles if resources are limited.
Compatible with caution
Clown Triggerfish
Balistoides conspicillum
Triggerfish have powerful jaws designed to crush and consume crustaceans, making the hermit crab an expensive snack.
Not recommended

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