I have done the research now and here are the facts:

Blanket/string weed grows and feeds on calcium in the water, so it is difficult to get rid of, pulling at it breaks off the weed, but tiny fragments of it float in the water then it grows again.
There is a plug in device called electronic blanket weed controller. This unit is plugged into a socket, it has two sensors coming out of the box that you wind around the hose that feeds water into the pond, these sensors omit an eletrical current that disrupts the formation of calcium, therefore the weed breaks down and can no longer grow in the pond.
I bought one and IT WORKS!!!!!!!!!!!!!!