Scarlet reef hermit crab (Paguristes cadenati) care guide

Group
Other invertebrates
Other names
Scarlet hermit crab, Red reef hermit crab, Red legged hermit crab
Family
Diogenidae
Origin
Caribbean, Gulf of Mexico, southern Florida and the West Indies; coral reefs, intertidal to about 80 m
Water
saltwater
Maximum size
3.8 cm
Temperature
22–26°C
pH
8.1–8.4
Hardness
dKH 8–12, SG 1.020–1.025
Care level
beginner
Temperament
peaceful
Reef safe
yes

Care

The scarlet reef hermit crab is a small hermit crab with a bright red body and legs, deep red antennae and yellow eyestalks. It is about 3 cm long (LiveAquaria lists up to 3.8 cm). The left claw is slightly larger than the right. It can be confused with the orange-claw hermit (Calcinus tibicen), which is darker with white patches near the leg tips. It is named after the French ichthyologist Jean Cadenat. It lives on Caribbean and Gulf of Mexico reefs and coral rubble. It is hardy and suits any established reef. Water: 22–26 °C, pH 8.1–8.4, dKH 8–12, SG 1.020–1.025. It does not tolerate big swings in water parameters. Clean-up role: it is one of the most popular reef clean-up crabs, eating filamentous and hair algae, slime algae and cyanobacteria, as well as detritus and leftover food. LiveAquaria gives no stocking rate; a common guide is roughly one per 20–40 litres. Hermits need spare shells: keep several empty shells slightly larger than the ones they wear (ceriths and similar), or they may kill snails to take their shells. If algae runs short, feed dried seaweed or marine pellets. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never dose them in a tank holding this animal, and check the label of any treatment or fertiliser before use. Sources: LiveAquaria (liveaquaria.com/products/scarlet-reef-hermit-crabs); Wikipedia (en.wikipedia.org/wiki/Paguristescadenati). Checked October 2026.

Diet

Omnivorous scavenger: filamentous, hair and slime algae, cyanobacteria, detritus and leftover fish food. Supplement with dried seaweed, algae wafers and meaty marine pellets when natural food is scarce.

Breeding

Separate sexes; it breeds all year. Females carry orange eggs that hatch into planktonic larvae, which later settle on the seabed and must find a shell. Larvae are not raised in home aquaria.

Compatibility and tank mates

Reef safe and one of the more peaceful hermits: it does not harm corals or fish. Without spare shells it may attack snails for their shells, and hermits can squabble over shells. Eaten by triggers, puffers, hawkfish, large wrasses and large crabs; keep the tank free of such predators.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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