Invertebrates: Crustaceans (Crabs) Part II

Crabs are opportunistic feeders, so care should be utilized in all cases. If they are not fed adequately, they will find food in the form of snails, fish, etc. Crabs grow by molting, so it is not uncommon to see what appears to be a dead crab in the aquarium with the real crab hiding to protect its soft new shell.



White Spot Reef Hermit Crab (Dardanus megistos) – Not Reef Safe
This beautiful hermit crab is far from reef safe as it can grow extremely large, be extremely predatory, and also be very destructive. It is best kept in a fish-only (species limited to those that will co-exist of course) or species-specific aquarium. They can also be housed in larger sumps with regular feedings.
White Spot Hermit Crab
Xanthidae Crab:  Not Reef Safe
Since there are several hundred species in the family Xanthidae, identifying this particular crab to the species level is rather difficult.  However, black-tipped claws are a good indicator that this crab was bad news (not all black-tipped crabs are bad though).  Xanthid crabs typically enter the aquarium world by hitchhiking on live rock or corals.  They use their strong claws to enlarge hiding spots in the rock, which ultimately weakens the rock.  Even worse if they decide to nest in a coral since they will carve out a hole and destroy the surrounding tissue.  Xanthid crabs are known to eat almost anything and are very destructive in the process.  Recommend removal from a reef aquarium as soon as possible.  Occasionally soda bottle traps work, but typically homemade spears work best.  If removed safely from the reef aquarium, I recommend keeping these crabs in a species-specific tank or suitable sump as they are very interesting to watch.
Xanthid Crab
Gorilla Crab (possibly Pilumnus vespertillo):  Not Reef Safe
This is another example of a Xanthid crab (the black-tipped claws are hidden under its body.)  This is one of the many crabs that falls under the generic name, “gorilla crab”.  Recommend relocation from a reef aquarium to a suitable sump or species-specific tank.  See above for more information.
Gorilla Crab
Teddy Bear Crab (possibly Polydectus cupulifer):  Not Reef Safe
This is another example of a Xanthid crab, and this is one crab that frequently falls under the common name, “Teddy Bear Crab.”  It is also frequently called a “Gorilla Crab”.  See above more more details/warnings on Xanthid crabs.
Teddy Bear Crab
Pom Pom Crab (Lybia tessellata):  Arguably Reef Safe
Pom Pom Crabs are…well…just awesome.  They are beautifully colored, carry anemones for protection, and act like boxers about to take a swing.  They carry the anemones on the tips of their claws for protection.  If they feel threatened, they will sway their arms out, and will occasionally strike an opponent with the anemone.  In exchange for the anemone’s protection for the crab, the crab helps feed the anemones.  The crab’s anemones may sting and damage typical reef inhabitants (corals, crabs, fish, etc.), so caution is urged.  However, this crab can be rather secretive, so potential damage is limited.

Pom Pom Crab

Photo Source: Kevin Youngberg (aka Fatman)

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  1. Daiara

    thank you for sharing some knowledge. i really appreciate it.

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