Are you talking about the stringy green strands in between the aipastias? If so looks like algae to me and might be bryosis(sp?) which is a devil to get rid of if it grabs a good hold of your tank. I would also do something about those aipastia anemones, they also will spread like wildfire if given the chance. DO NOT cut or rip them off though, they will spread even faster that way. I use aipastia X and inject the solution into the mouth and totally cover it til its gone. Turn off the water flow too if you decide to nuke them.
Here is a great link that can help you identify the algae if thats what it is.
http://www.reefcleaners.org/index.php?option=com_content&view=article&id=54&Itemid=60 Hope that helps