Can anyone name this weed? Best treatment in a high alkalinity waters (340 ppm)?

Neighbors have been fighting this in their pond for years, it keeps returning and getting stronger.
Has the look and feel of fiberglass insulation, no smell, starts on bottom and floats in mats.

Thanks,
Joe

That's our old friend Mr. Filamentous Algae (FA).

If it's a consistent problem year after year, you may want to consider stocking Tilapia annually.

If you are not opposed to pond dye and there is not a large amount of water flowing through the pond, apply dye after ice out before it can start growing.

Stay tuned for suggestions for chemical treatment.

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=534880#Post534880
Heres a link to a thread which it is discussed. It can be managed but just left alone prolly will get worse.