What is this?
 

I have this growing on my live rock and i dont know what it is?
Anyone?

Attachment 3015

Attachment 3016

I appears to me to be sargassum algae
http://www.melevsreef.com/id/sargassum.html

and for any other critters you need to ID

http://www.melevsreef.com/id/

That looks like it, only mine is green. Thanks for the link.

Yep, that's Sargassum...yank it. It will grow like a big, bad, ugly weed. :(

Consider it done! Thanks.

No problem! :) I fought with Sargassum in my tank for a few months. The stuff will keep coming back.

we have tons of that stuff growing on our rocks too. It's a real pain to try and get rid of it, especially if you have a new system like ours. I sure hope that it dies off soon. Good luck!