In the UK I think we call it 'Blanket' weed. Evil nasty stuff to get rid of, but over a decade of trying different things, Blanket Answer is utterly amazing! Even with 18 inch long strings of algae this stuff just dissolves it all. Makes the water milky for a day or so but not a single fish has ever complained.
Last few years just a treatment in Spring and the algae is gone for the rest of the year. Seriously Blanket Answer is the very best stuff out there. IMHO.
pond filter I use this external filter and it is great also try using this pond algae killer it kills off sting algae all you do is mix it in a bucket of water and tip in in your pond. It is an expensive fix but works perfect. I would also recommend a pressure washer to clean the filters.