I need an ID on a pesky algae that I have been fighting with

[ogopogo]

I have tried manual removal, even to the point I have pulled out bad rocks, it does help, and a lot, but the root system on this stuff is everywhere so I don't seem to have luck getting it all.
As for urchin, I have a pincushion. I'm not saying he doesn't touch the algae, but he doesn't eat it fast enough. I do also have 2 emerald crabs in the tank I forgot to mention.
Thanks again for all the help folks!!