What is this coral?

[207Meg]

I added a few snails, who had some coral on their shells and it spread to the rock. It's really dainty/pretty. Light brown with blue dot at center. Very small, smaller than pencil erasure. Slow to spread. Any idea what it is?

 

[Troylee]

Clove polyps.. most would say invasive as you have seen how fast they spread! They can take over a tank quickly lol..