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Scarlet Reef Hermit Crab© Andreas März from Darmstadt, Germany / CC BY 2.0

Scarlet Reef Hermit Crab

The Scarlet Reef Hermit Crab is a small Caribbean hermit crab known for its vivid red legs and bright yellow eyestalks. It readily grazes on filamentous algae and cyanobacteria, making it a reliable cleanup crew member in a mature reef tank. Among hermit crabs, it stands out for its gentle, easygoing temperament and generally gets along well with tankmates. Keep a few spare shells on hand for it to move into, and this species is an approachable choice even for those new to the hobby.

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About Scarlet Reef Hermit Crab

A small Caribbean hermit crab that grazes on algae as a reef tank cleanup crew member. Gentle and easygoing, making it approachable for beginners.

7 things to know before welcoming a Scarlet Reef Hermit Crab

  1. 1Keep spare shells ready

    As it grows, it will outgrow its current shell and need to relocate. Keeping several empty shells of varying sizes on hand allows for a smooth move after molting and helps prevent stressful shell-fighting with tankmates.

  2. 2Its role as cleanup crew

    It readily feeds on filamentous algae and cyanobacteria, making it well suited to algae control in a mature reef tank. That said, if algae growth in the tank is limited, supplemental feeding may be needed.

  3. 3Gentle and reef-community friendly

    Among hermit crabs, it is relatively non-aggressive and generally coexists well with other crustaceans and small fish. It is also considered unlikely to bother corals or other invertebrates.

  4. 4Avoid disturbing it during molting

    It molts periodically as it grows, and during this time its body is soft and vulnerable. If you notice signs of molting, avoid handling it or disturbing the tank unnecessarily.

  5. 5Prepare a stable tank before adding one

    It does best in a reef tank with stable water quality and temperature. Acclimate it carefully before introducing it, since sudden changes in water parameters can affect its health.

  6. 6Know its maximum size

    Even as an adult, this species stays small, reaching a maximum body length of about 3.8 cm. There's little concern about it outgrowing the tank, making it a comfortable fit for small to medium reef setups.

  7. 7Approachable for beginners

    Thanks to its hardiness and calm temperament, this species is considered suitable for beginners. With basic water quality management and a supply of spare shells, it's an approachable species to start with.

Frequently asked questions about Scarlet Reef Hermit Crab

Q.Can it be kept with other tank inhabitants?
A.Thanks to its gentle, low-aggression temperament, it generally mixes well with other crustaceans and small fish, and is considered unlikely to bother corals or other invertebrates. That said, individual behavior can vary, so it's worth observing it after introduction.
Q.What should it be fed?
A.It readily eats filamentous algae and cyanobacteria, so in a mature reef tank, naturally occurring algae can serve as its main food source. If algae in the tank is limited, consider offering supplemental feeding.
Q.How should shells be prepared for it?
A.Since it relocates as it grows, it's important to keep several empty shells of different sizes on hand. Without a suitable shell available, it may be unable to relocate, which can become a source of stress.
Q.How difficult is it to keep?
A.It's considered a beginner-friendly species, hardy and easygoing enough to be manageable for new keepers. With basic water quality management and a shell supply in place, it's an approachable species to start with.
Q.Is it subject to any regulations?
A.This species is not subject to CITES.

Useful tools for Scarlet Reef Hermit Crab care

💧Aquarium Volume CalculatorCalculate water volume, weight, and heater wattage from tank dimensions🧪Water Quality CheckerFind compatible fish, shrimp, plants & corals based on pH, temperature & hardness🍽️Feeding GuideCheck feeding frequency, portion sizes & supplements by species and growth stage🤝Compatibility CheckerCheck compatibility between two species on a 5-level scale📊Fish Compatibility MatrixCheck fish compatibility at a glance with our matrix chart🔄Nitrogen Cycle GuideAuto-calculate bacteria colonization timeline for new tank cycling🗓️Seasonal Care CalendarMonthly care events and seasonal management tips at a glance🚿Water Change CalculatorAuto-calculate optimal water change frequency and volume by tank size and fish count🐠Stocking CalculatorCalculate max fish capacity for your tank size with overstocking alerts🏞️Tank Layout PlannerGet substrate, plant & hardscape suggestions based on tank size and style🧮Care Cost SimulatorEstimate initial, monthly & annual costs by category, care level and quantity⚖️Species Comparison ToolCompare two species side by side: care difficulty, size, lifespan & temperature🎯Pet Match DiagnosticAnswer 7 questions to find your top 3 perfect pets🚚Transport Safety CheckerCheck transport safety score and precautions by category, season, method and distance⏱️Quarantine & Acclimation TimerManage quarantine periods and acclimation steps with countdown timers. Includes recommended durations by species

Learn more about Scarlet Reef Hermit Crab in the encyclopedia

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Care difficulty, lifespan, size and diet — all basics covered.

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