Hi Spooky.Is it in both ponds? I have never had any problem with blanketweed in the nature pond as it is so well planted.Generally if you are not keeping and feeding fish, there are no waste products feeding the wretched stuff.Much more difficult with the fish pond.You need to remove as much as you can manually and it is hard work.Every day is not too often.Block out sunlight which is also a major cause,by planting up lots of weed and floating plants.When the water lily leaves get to the top this will also help.An algae bloom is very common this time of year.
You can treat the pond with Interpet pond balance which is a very naturael treatment and alters the PH to make the conditions harder for blanketweed to grow.But it sheer persistence that pays off.I would buy some more plants and weed,a very good one is Hornwort which does not need planting as it doesn't have roots ,but it grows well all summer then sinks to the bottom over the winter.
Another tip,especially if you have a waterfall ,is to root water cress in glasses of water in the house,then throw it into the pond,or waterfall and it will greedily feed on the excess nutrients,such as the nitrates.