hermit crab on acan lord coral image via reef2reef member @Mr. Microscope

Crabs are an essential part of the Red Lobster menu, but they play an even more important role in quite the opposite way in the wild and even your aquarium. Some types of crabs are pure evil when it comes to reef friendliness, but others are amazingly beneficial. Some crabs even rely on the well being of certain corals to thrive. When you want crabs, get the kind that won’t irritate you. You will frequently get hitch hiker crabs that you will have to deal with before you add what they came on to your tank. Gorilla crabs seem to be the most common coral munching crab these days. They resemble an Emerald Crab, but are more brown with black tipped claws. DO NOT LET ONE IN YOUR TANK!!!! Now, onto some cool crabs that are safe!


emerald crab image via flickr member @herebirdiebirdie

Emerald Crabs: These are those jolly green fiddler-crab-like, bubble algae munching guys that are very common. Almost every LFS has them in stock and most aquariums have at least one living in them. They eat all day. They don’t mess with corals or fish, but in some cases have been reported to when full grown. This may have been due to lack of available food, but the risk is still a possibility. Most people will toss theirs into their sump to clean the refugium, granted there are no corals there.


arrow crab image via jaxshells.org

Arrow Crabs: These are one of my favorite crabs to watch. They are shaped like something you would see in a cartoon, and colored to suit. The pinstripe pattern is quite a contrast to their gumdrop body and long, daddy longlegs-like appendages. These crabs are considered 50/50 when it comes to being reef safe, so be prepared to part with yours and try again with a new one.


pom pom crab image via bio390parasitology.blogspot.com

Boxer or Pom Pom Crabs: These are very cool. They are small, so try to limit their tanks to 30 gallons maximum or you may end up losing them. They carry 2 small anemone in their claws, resembling pom poms, but the use them like a boxer. They rarely go after fish or other inverts unless they feel threatened and even then they mainly just show off each others scary pose and the confrontation ends.


bluelegged hermit crab image via ultimatereef.net

Hermits: There are plenty of hermits, but which ones are safe? The blue legged are the most common and docile, though every hermit needs a shell and if it has to rob a snail it will…bottom line. Do not get attached to your pet snails if you plan on having hermit crabs or you will be sad when ol’ turbo is found on the back of a crab. Sticking to the smaller sized crabs is the best bet, as the larger crabs tend to be, at the very least, clumsy and able to knock things over. Some may even hunt fish or munch coral. Most just eat detritus, algae, and any other scraps they can find, hence their Janitorial status.


decorator crab with mushroom image via .kudalaut.eu

Decorator Crab: NOT REEF SAFE. This is an important crab to avoid, since they are very affordable. You may have seen them at the LFS covered in rubble and shells, but they are not limited to the fashions they are stuck with their. Every crab molts, therefore losing their particular arrangement of camouflage. Some crabs will actually molt and then pluck off the stuff off their old skin and reuse it, but most likely they will want to blend in with where they are currently living. If you have a coral inhabited tank this means the possibility of a coral fragging crab. They are not afraid to stick a few zoanthids to their bodies. They may even eat your fish. These are also seen as hitch hikers as well so be cautious with your purchases!

These are merely a small handful of available crabs. Each crab has its own purpose and risks. For more crabby knowledge without the crabby attitude check out our awesome (INVERTEBRATES FORUM).

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