Scarlet Reef Hermit Crabs

Quick facts

Identity

Also known as

Red Reef Hermit Crab; Red Legged Hermit Crab; Scarlet Hermit Crab

Environment

Saltwater

Native to

Caribbean Sea, Gulf of Mexico, southern Florida, West Indies

Habitat

Coral reefs and rubble zones, from the intertidal zone down to about 80 m depth

Sourcing

Wild-caught

Conservation

Not Evaluated

Care

Care level

Easy

Temperament

Peaceful

Adult size

0.8 – 1.5 in (1.9 – 3.8 cm)

Lifespan

2 – 4 yrs

Min tank

10 gal (38 L)

Growth rate

Slow

Placement

Bottom

Water

Temperature

75 – 79 °F (24 – 26 °C)

pH

8.1 – 8.4

dKH

8 – 12 dKH

Salinity

1.023 – 1.026 SG

Flow

Moderate

Behavior & compatibility

Social

Group

Aggression to own kind

Low

Active

Night

Reef safe

With caution

Invert safe

With caution

Shrimp safe

With caution

Clean-up role

Algae, Detritus, Leftover food, Biofilm, Sand sifting

Population boom risk

Low

Feeding & breeding

Diet

Omnivore

Foods

Algae, Biofilm, Frozen, Freeze-dried, Pellets

Breeding type

Larval (brackish)

Breeding difficulty

Not bred in captivity

Sexing

Sexes are separate but not externally distinguishable without dissection

Target feeding

Beneficial

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Care guide

Overview

Collected from reef and rubble zones across the Caribbean and Gulf of Mexico, this small scavenger carries bright red legs and a yellow face into any established saltwater tank. It works rock and sand for hair algae and detritus, needing little supplemental feeding, and molts periodically, requiring a steady supply of spare shells. Sensitive to copper and salinity swings, it does best in mature, stable systems.

Care

This small scavenger settles in quickly once a tank has matured, spending most of its time working over rock and sand for algae and leftover food. It tolerates a wide range of reef parameters but is sensitive to copper and sudden salinity swings, so top off with fresh RODI water rather than saltwater. Because it periodically molts and outgrows its shell, keep a rotating supply of empty gastropod shells of varying sizes on hand at all times.

Feeding

In a well-stocked reef system this crab forages mostly on hair algae, film algae, cyanobacteria, and detritus, needing little direct feeding. When natural algae growth is scarce, supplement with dried seaweed, sinking pellets, or bits of frozen seafood so it does not turn to grazing on coral tissue or snail shells. Feed a small amount several times a week rather than large infrequent portions to avoid fouling the water.

Tank mates

Generally peaceful toward fish and corals, though it may walk over polyps and occasionally pick at LPS food, and it will compete with or bully snails and smaller hermits for shells if none are spare. Avoid keeping it with aggressive shell-collecting hermit species or predatory fish such as triggerfish, larger wrasses, or puffers that will eat it. Providing abundant empty shells reduces conflict with tankmates considerably.

Breeding

Breeding occurs year-round in the wild, with females carrying orange eggs that hatch into planktonic larvae before settling and seeking their first shell. This larval stage makes captive breeding essentially unfeasible in a home aquarium, and no reliable aquarium breeding protocols exist. Specimens in the trade are collected as adults rather than raised from larvae.

Health

Most losses trace back to poor acclimation, unstable salinity, or a lack of suitable shells rather than disease. Molting is a normal but vulnerable period during which the crab may hide and become inactive, and it should not be disturbed or removed at this time. Watch for repeated shell abandonment, prolonged lethargy, or failure to right itself, which can signal stress or a shell that no longer fits.

Sources

1. Paguristes cadenati - Wikipedia
2. Scarlet Reef Hermit Crab: Saltwater Aquarium Invertebrates - LiveAquaria
3. Scarlett Red Hermit Crab Care Guide | Top Shelf Aquatics
4. Caresheets - Scarlet Reef Hermit Crab - Fishkeeping

Varieties in the catalog

Dwarf Red Tip Hermit Crab

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