Mystery Critter on glass

[jbd]

Any idea what this is? Many of different sizes on glass, none bigger than 2 mm. (pic is through magnifying glass)

 

[KJ]

Hydroids medusa. Not a problem except in breeding tanks.

 

[jbd]

I see. A kind of "jelly fish." Thanks. I never see any swimming around in my tank, so I guess they don't survive to maturity. Do they get swept up the the skimmer or are they food for my LPS coral? I have one Yellow Tang and two cleaner shrimp as well.