I have no idea where this came from. The only new thing I have added recently were clownfish and an acro from reefstock and an acan frag a few days ago. The acro is fairly close to this area, but the acan is across the tank. Here are a couple of pictures. The first was yesterday, and the second this morning, so obviously it moves. If anyone knows what it is please tell me what it is and if I need to do anything. Thanks everyone!
View attachment 12645
View attachment 12646