Cymo melanodactylus:Checking for a local. At first was recommending sump or dump due to the black claws, but they sent a zoomed in photo and the claws look a bit too spoon-shaped for me to say "gorilla crab" with confidence.
@ISpeakForTheSeas any chance this is a mithrax crab or similar? I.e., reef safe-ish or bad guy? Thanks!
The link below is about a closely related species, but gives a bit more balanced of an idea of the semi-beneficial semi-parasitic relationship of these crabs with their host corals:That said, there are also reports like the one linked below where the crabs may be responsible for killing coral colonies.
However, the corals dying may have been caused by a few separate things:
-Overpopulation of crabs
-Disease
-Bleaching
-Etc.
If the corals were dying for reasons unrelated to the crabs, however, then the crabs may have been trying to protect the healthy colonies by consuming the sick/dying ones.
So, the crab is essentially typically a beneficial parasite; if the coral is small or struggling in your tank, then the crab could very well kill it, but if it's large and doing well, it should be fine to keep.
