This rock has been in the tank for maybe 6 months. The tank has been fallow for many months because I hadn’t decided what I wanted to do with it. The only new thing I added recently was some live sand. Now this started growing. It’s like it has polyps and tentacles.
I think you may be right. I've never seen them in person though. They are now under super glue and a piece of cellophane. I'll let them die and then remove the whole bunch.