I have been in the hobby almost as long as Bill. and have never seen an algae like this before if it is an algae. it is solid brown and almost like bubbles but not quite! it is Gelatinous in nature but sticks to the rocks really well. It showed up on an area of rock after I moved a power head that pushed a strong flow across it. I am cleaning the aquarium tomorrow and plan on removing as much as i can.. just worried this might spread it.. wish I had pics but I have almost given up on taking pics of this tank