Please ID this

[kwan]

Something has been growing over my xenia and is killing them. As you can see in the photo, it is a web like plant. It grows rapidly and it seems to be growing on other LR as well. Is it something I should worry about?

 

[quarryshark]

Maybe Halymenia.
http://www.reefs.org/hhfaq/pages/main_pages/faq_algae.htm

 

[kwan]

I am not sure if it is Halymenia. Mine seems to be hollow inside and covers just the surface. It would worry me if it has a chemical defense system. My tangs won't eat it at all.

 

[Fluff]

It does look like some type of macro. I'm not sure what kind though. Some type of Gracilaria maybe? Here are some macro sites for you to check out.

http://www.botany.hawaii.edu/GradStud/smith/QUEST/limu-studyguide.htm

http://omp.gso.uri.edu/discovery/biota.htm#alg

http://www.wetwebmedia.com/brnalgae.htm

 

[kwan]

Not sure if it is Gracilaria either. Mine doesn't seem to have any branches and it doesn't grow upwards. It is more web like and blankets the surface in a single layer. I agree it is some kind of macro, just can't find a match though.