Any idea what this is?

[Terri Caton]

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.

 

[Redfoxtang]

Almost looks like hydriods.

 

[Terri Caton]

Almost looks like hydriods.

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.

 

[Crabs McJones]

I agree, cluster of hydroids