Eco Pure added weekly will reduce blanket weed by reducing its food source.  Bacteria coat the blanket weed starving it of food - this will initially break up long strands.  Every pond is different! In some ponds Eco Pure can work in 2 weeks, most ponds can take 4 to 8 weeks.  Use Eco Pure early in the season - do not wait for it to grow, in other words use it in a regular preventative approach.