Unknown Critter

[Mflores888]

My friend found this in his tank, and we have no idea what it is. He says it crawled out of the meat coral he has but I honestly dont know anything that would do that. Any help would be appreciated

 

[tsouth]

Research tells me this is known as a Gall crab. I do not have personal experience on it's safety within the aquarium so heeding giving advice here. Good luck!

 

[king aiptasia]

Gall crabs are obligate symbiotes of corals, they induce the corals to grow into a housing structure for themselves. I cant say I've heard of them killing corals in aquariums (any input would be appreciated here) but they can slow down growth around the "gall spot". they tend to survive off of coral mucous, coral fecal matter and plankton, also scavenging on the coral surface