I have had this beautiful rock of Zoanthids with at least 4 different kinds on it, but ever since I got it the polyps started dying off. It made no sense to me - Zoanthids are not hard to keep, and my water parameters were very good. It was not until 5 months later, yesterday night, that I saw out of the corner of my eye the cause...

A light brown crab the size of a toony with black pinchers was pinching off each polyp one by one, eating them. Right in front of my eyes. So I promptly stuck my hand into the tank and grabbed it, hoping that it would not try to pinch me. Got it out, and in to the mantis tank. I heard one loud click as the mantis shrimp smashed it, but I do not think the crab got hurt. Will see if he gets eaten.

Here is a picture of the crab. He became dinner yesterday night. It was actually quote cool to see how the mantis shrimp took off a pincher each night, and ate it. Then left the body for last. So this crab fed him for a week.