i have blanket weed every year, ive tried all sorts to get rid of it but with no luck, i tend to just pull it out and leave it on the side for a couple of days then put it on the compost heap. my pond is quite shaded but it still grows like wildfire, i think that once you have it its impossible to get rid of it completly unless you start from scratch with all new plants, and even then you cant garentee it wont appear again as the spores are carried on plants and wildlife. i think its just a case of keep it down to a minimum any way you can. good luck.