Digitate Hydroids??

[AlabasterEskies]

So a couple days ago I spotted a little grouping of these dandelion looking things on one of my LRs. well I have been searching the net for an ID and I think they are Digitate Hydroids. What I can't seem to find is a good description of what they are, if they need to be eradicated, and if so how.
Also this evening I notice one of my cerith snails is absolutely covered in them!

they kind of look pretty on the rock but on the snail shell they make my skin crawl! I can't get a picture of the snail yet, but here is a couple shots of the rock (sorry about the poor quality)

~jen

[GoTakuF1]

Here's a short loose description of: Hydrois.

Here's a guide on removing hydroids: Getting Rid Of Brown Hydroids.