Not furry either, still lovely.
Scarlet Reef Hermit Crab
Paguristes cadenati
Also called Scarlet hermit crab, Red reef hermit crab
From Coral reefs of the Caribbean Sea and Gulf of Mexico, including southern Florida and the West Indies, from the tide line down to about 80 m.12
A friendly guide, not veterinary advice. For anything about your pet's health, ask your vet.
At a glance the quick version
Wikipedia gives about 3 cm across; LiveAquaria gives a maximum size of 1.5 in (3.8 cm).
Looks how to spot one
Hard front body with a soft abdomen kept inside a borrowed snail shell
A bright red hermit crab with deep red antennae and yellow to yellow-orange eyestalks, giving it a yellow-faced look. Like all hermit crabs it lives in an empty snail shell and swaps up as it grows.12
Personality what they are like
A peaceful scavenger that gets along with tankmates and spends its time picking over rocks and sand for food.2
Daily activity how busy a day looks
Busy and always foraging over rockwork and sand. It needs room to roam and plenty of surfaces to graze.21
Grooming and care the hands-on bits
Rated easy. Keep spare empty shells in a range of sizes so it can move house after moulting. Keep water stable and avoid copper-based medications.23
Home where they are happiest
An established reef aquarium. LiveAquaria gives 72-78 °F (about 22-26 °C), pH 8.1-8.4, dKH 8-12 and specific gravity 1.020-1.025. No minimum tank size was given by the sources.2
Food basics what goes in the bowl
An omnivorous scavenger of plant and animal detritus. In aquariums it grazes hair, filamentous and slime algae plus cyanobacteria; add dried seaweed and small marine foods if natural food runs low.12
Company who they like around
Often kept in small groups as part of a clean-up crew, and peaceful toward other tank residents. Extra empty shells help keep things calm.21
The story where it all began
Jacques Forest described the species in 1954 and named it after Jean Cadenat, the French ichthyologist who collected the type specimen. It is now one of the best-known reef-safe hermit crabs in the aquarium hobby.1
Fun facts for the dinner table
- 1
Young crabs are picky about housing and favour empty shells of Cerithium and Vasum snails.1
- 2
It breeds all year round in the wild, and its orange eggs hatch into drifting plankton larvae.1
- 3
It is easy to confuse with the orange-claw hermit crab, which is darker and has white patches on its leg tips.1
- 4
Hermit crabs sometimes line up by size beside a new empty shell and swap homes one after another in a 'vacancy chain'.3
Recognised by the official bits
- Taxonomy (via Wikipedia)
- Described by Jacques Forest in 1954 and named after French fish scientist Jean Cadenat, who collected the first specimen; family Diogenidae.1
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Scarlet Reef Hermit Crab. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingDepends on species, many feed from the light and the watervaries
- Salinity checkevery week
- Water testevery week
- Top-upTop up evaporation with fresh RO water, not salt waterevery day
- Water changeAbout 10 to 20% of the waterevery 2 weeks
- Light checkevery month
Owner questions the things everyone asks
How often should I feed my Scarlet Reef Hermit Crab?
Feed only when natural algae runs low, offering a small piece of dried seaweed or a tiny marine pellet every couple of days. Overfeeding can dirty the water, so watch your crab's activity and adjust. Furry Diary's starting plan suggests feeding depends on the species, as many feed from the light and water.21 Furry Diary plan
What does a Scarlet Reef Hermit Crab eat, and what should it never eat?
It eats algae, cyanobacteria, and small marine foods like dried seaweed. Never give copper-based medications or foods with copper, as these are toxic to invertebrates.213
How much space does a Scarlet Reef Hermit Crab need?
No minimum tank size is given, but it needs room to roam over rockwork and sand. A small group in an established reef aquarium works well, with plenty of surfaces to graze.21
What temperature, light or water does a Scarlet Reef Hermit Crab need?
Keep water at 72-78°F, pH 8.1-8.4, dKH 8-12, and specific gravity 1.020-1.025. Normal reef lighting is fine, and Furry Diary suggests checking lights monthly and topping up evaporation daily with fresh RO water.2 Furry Diary plan
How often should I clean a Scarlet Reef Hermit Crab's home?
Furry Diary suggests a 10-20% water change every two weeks and a weekly salinity check. Also test water weekly and top up evaporation daily with fresh RO water. Furry Diary plan
Can a Scarlet Reef Hermit Crab live with others?
Yes, it is peaceful and often kept in small groups as part of a clean-up crew. Provide extra empty shells in various sizes to prevent shell fights.21
How long does a Scarlet Reef Hermit Crab live?
Lifespan varies and is not specified in the sources. Ask a good breeder or an exotic-pet vet for more details.
Can I handle a Scarlet Reef Hermit Crab?
Handling is not recommended as it can stress the crab and damage its delicate body. Observe it foraging in the tank instead.23
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Furry Diary's own starting care plan. A friendly guide, not a vet's advice.
You might also like
Caribbean Hermit CrabLike what we are building? Buy Archy a bone.
All of this is free for everyone, with a source on every fact, and it will never show annoying ads. It was a big job to build, so if it helped you, buy Archy a bone. Any amount is lovely, and no is a perfectly fine answer too.
Archy is our Australian Cattle Dog and chief taste tester. Tips go to 4V3D OÜ, the small family studio behind Furry Diary.
Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at support@furrydiary.app and we will fix it.
- Paguristes cadenati (Wikipedia) en.wikipedia.orgused for names, range, depth, size, colour, diet, taxonomy, fun facts
- Scarlet Reef Hermit Crabs, LiveAquaria liveaquaria.comused for care level, water parameters, diet, size, shell needs
- Hermit crab (Wikipedia) en.wikipedia.orgused for shell swapping and vacancy chains
- VCA Animal Hospitals: Feeding times and frequency for your dog vcahospitals.comused for owner questions
- ASPCA: Dog grooming tips aspca.orgused for owner questions
- ASPCA: Cat grooming tips aspca.orgused for owner questions
- ASPCA: People foods to avoid feeding your pets aspca.orgused for owner questions
- RSPCA: What to feed your rabbit rspca.org.ukused for owner questions
Checked 2026-09-30. Text is written in our own words from these sources.