Coral Destroyer Crab

Zakary2003 · Oct 19, 2023

I recently posted about a concerning decline in my reef tank corals with seemingly no cause. My parameters have always been good and stable for the most part. I was very confused because an entire colony of 12+ rasta zoanthids and a smaller frag with 3 polyps disappeared overnight, but that was just the most recent case of mysterious coral decline. Well, I decided to look around with the lights on red and found this guy munching on my candycane coral, and I think he is the culprit. I turned on the UV channel and sure enough, he was taking large florescent chunks of tissue off the coral and eating it.That is the coral closest to the disappeared zoa colony. He has already been removed from the tank and disposed of as humanly as possible, but I am wondering what he was. He must have come in on my liverock from Florida, or I guess he could have survived my coral RX and hyposalinity dips. Can anyone id it? I know the pictures aren't great.

Midrats · Oct 19, 2023

Perhaps a red mithrax. I have had a few come on Florida rock but never had any problems with them. I feed a lot, maybe that's why they leave my coral alone. They do destroy bubble algae for me.

The_Paradox · Oct 19, 2023

Looks a little like a juvenile male king crab. You have a better picture if the carapace?

Zakary2003 · Oct 19, 2023

The_Paradox said:
Looks a little like a juvenile male king crab. You have a better picture if the carapace?

Those are the only two pictures I have. Aren't king crabs cold water?

Zakary2003 · Oct 19, 2023

Midrats said:
Perhaps a red mithrax. I have had a few come on Florida rock but never had any problems with them. I feed a lot, maybe that's why they leave my coral alone. They do destroy bubble algae for me.

I have a red mythrax crab. He's an absolutely character. This guy doesn't look quite like him. Smaller claws, bigger carapace, more of a pattern.