Has this happened to you?

Just remember to get a red filter for it because the red tends to not wake up the fish and it should not scare away your findings. About 2 hrs after the lights go out is my favorite time to check out the critters.

 

If it where me I'd just plan on getting the crab out asap. Not many crabs I'd trust hell none really I have seen all of them go nuts sometimes and eat what ever they wanted All crabs are omnivores and will eat what they can when they are hungry from hermits to box crabs I trust very few of them and and not totally and as I said I have seen them all eat what I did not want them to eat.. Thats another reason I use a few hermits as needed to keep the system clean. I don't want to over feed the tank to keep them from getting hungry.. Might want to see if the rock came from the gulf or Caribbean area ? Good luck