Pls help identify

[shanet1975]

I have around 11 rocks covered with whatever is in the picture attached below. It is also crawling up the back wall. They seem to be little hand like things that don't seem to harm anything and close up when touched or when lights are out. Please let me know if you need a closer picture.
Thanks...

 

[pimpinitup6969]

star polyps! a soft coral that will over run your tank if you let it!

 

[shanet1975]

Thank you.....
I like them, but not as much as I have. Or more. Is there any way to control it?

 

[pimpinitup6969]

not really they are pretty invasive! but they pull off the rock in mats pretty easily! so when they get bad trade them to other reefers or to your lfs for credit