Black stuff on rocks

[MmmmBalf]

After I finally got rid of a large dino problem, I had a huge GHA outbreak with the increase in nutrients from the dinos. Now the GHA seems to be dying off, growing brown & patchy etc. As this has started, I'm getting patches of black stuff on the rocks, under the GHA. It's unsightly (as if the GHA wasn't bad enough. ;) )

Photos below. It scrapes off pretty easily with my fingernails, or pulls up with the GHA, and has a slimy sort of feel. Is this another type of algae? I'm in the process of ordering Vibrant, but that'll be a couple weeks delivery I imagine to Australia.

Thanks

 

[saltyfilmfolks]

How big is the clean up crew?