macro algae: pest?

nope / flame algae. same kind that john sells but that brown stuff ont he bottom id take a closer look if its sargassum its good if its diyochta.... depends. on if you want it.

but the brown looks like diychota.... so careful

If It is Diychota, I would yank it.

I accually like the look of it, but once it takes root in your tank, except burning it, theres really no way to get rid of it.

removal and burning the base area for a second with a blue jet flame lighter I am for.

natural removal methods exist but they are slow and boring.

Omg, are you guys serious about the flame part?