I've been having problems with what looks like the same stuff. I've been pulling it out for months - which I suppose is a positive in the sense that it tends to adhere to itself more than to plants and rocks, so if I grab enough of a clump, (visually at least) a lot of it comes away quite easily. It does anchor itself to gravel, so when I pull out a clump it carries away a few bits of 3-4mm gravel. Doesn't seem to anchor to plants in the same way as shown in the OP photo - I mention that because it might help identify it or differentiate from what the OP describes. That said my stuff does look very similar. - Though closer to Darrel's "it is usually shorter, darker green and a lot less "wispy" "
Having moved house recently, I haven't wanted to muck about too much. Indeed I had to back off my weekly water change routine as every time I changed water my crypts would melt as if they were adjusting to completely different water.
As the fish seem to be happy enough and the frogbit and various types of anubias growing OK (it's a low tech tank) I haven't been prioritising getting this sorted (plenty else to do when you've just moved house!) not least because at some point I've always planned to tear this tank down, but I'm glad to learn about Busan 77 / API Algaefix even so.
Reading the reviews on Amazon for API Algaefix the better informed advice seems to be completely in line with what Tom Barr is saying about minimal repeated 1/4 or 1/2 doses with the stuff already well mixed with a large volume of water and introduced during a water change.
Can anyone comment on the impact of this stuff on snails? I mean at 1/2 doses. The API label warns about crustaceans but not other invertebrates, and I like my snails