If you mean on your pond have you tried simply raking it off?

sorry yes its in the pond , we take out as much as we can on a regular basis , with a cane swirled round we have uvs and a filter the water on the whole is pretty clear plenty of plants and a couple of water lilys , it cloggs the pump up with in a week ,

My friends use a bale of barley (they have a huge pond) - you can get smaller amounts in nets from acquatic centres I believe. You just throw it in the pond and it miraclulously clears the weed.

Barley straw emits an enzyme as it rots down that supresses the blanket weed, my ghost koi are the best though.....they eat it....

I now get very little I use Barley straw, I tie mine on long twines and when they stop floating or turns black I replace them, which is every 5-6 months. Also I never add chemicals or tap water to my pond as I think it upsets the balance and makes things much worse.

Try cloverleaf blanket answer. It ain't cheap but it got rid of serious BW in my 3,000 gallon koi pond for 2 years. It's not a chemical either, it's an enzyme and eats the BW. Most koi keepers use it and most aquatic shops that sell pondfish should sell it.