Australian Institute of Marine Science - Coral Fact Sheets and ID Friday, 18 September 2015 21:26 Guest Coral Identification / Keeping
Although some hobbyist find crabs as interesting as I do, I have also learned that there are very few crabs that I would consider to be reef safe, about the only one that I have had experience with and can say they are totally reef safe are the commensal species, those that host either corals or anemone .
For crabs found living within tunnels/caves of live rock, the vast majority of them can not be considered reef safe, while most may not harm corals, they can do great damage to other sessile invertebrates that give meaning to the word "reef", coral safe, maybe, but not reef safe. Such crabs when small juveniles seem to help out by picking at algae and they, like many other inverts start out life as mostly herbivores but once they gain any size, they soon graduate to more meatier items on the menu. There are however crabs that are commensal with some coral genus groups and are a great help to the corals, these "coral crabs" are easy to distinguish from other types of crabs and should be left with their coral. To help identify such beneficial crabs, please see my Coral Commensal Crabs page.
I also see a lot of online stores and advice columns pushing hermit crabs as part of a clean up crew. It has been my experience that hermit crabs do not belong in a coral reef tank, they are omnivores as are all crabs, and its only a matter of time before hermit crabs figure out that there are meatier items available on the menu, namely your coral polyps and all types of worms. They are not invert safe as many will claim them to be. Except for the few commensal species mentioned earlier, all other free roaming crabs would be on my "get out of the pool" list for a reef aquarium containing other sessile invertebrates and/or corals.
REEF SAFE , either by their hosting a coral or anemone, or by their adult size remaining very small.
The Porcellanidae Crabs Photo Link #2 Photo Link #3 Can be considered Reef Aquarium Safe
The Anomuran crabs, part of the Porcellanidae family, relatives of Petrolisthes and Porcellanella.
The Galatheid Crabs
NOT REEF SAFE For fish only aquariums or those aquariums dedicated to keeping the more aggressive / destructive animals available, then some crab species can make for very interesting pets.
The Xanthidae Crabs (link - extensive photo gallery) None of which can be considered reef safe. Not only do they constantly enlarge their rock burrows, they will also roam your landscape at night picking off and eating just about all the life on your live rocks.
The Majidae Crabs ( spider crabs ) Also know as decorator crabs, these species are not only destructive with their feeding habits, but they are very likely to tear up any of your sessile creatures in an attempt to stick them to their backs in order to blend in with their surroundings.
Every Crab in the World
(click above link)
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