White stuff growing, what is it

[polarice18]

I dont have a picture of it yet. But there is this white stuff growing on my live rock. It looks like the white stuff that grows on dead fish but there isnt anything dead. they almost look like jellyfish, of course they are not. Anyone have any idea what they are or what they could be, and or if they are a hazard to the tank

 

[aldog51]

It is what we call a glass anemone or aiptasia. Read from this link: .Deleted. No website posting to other boards and advertizments and it will tell you exactly what they are and how bad are they