NT Labs Barleyclear is a great way to control algae and blanket weed naturally. A liquid extract which works by inhibiting the growth of green algae and blanket weed. Starts working immediately. Shake bottle well. This product cannot be overdosed. Mix the correct dose in a clean bucket of pond water, and then pour evenly around the pond. Control of blanket weed is best achieved by using Barleyclear before the water warms up in spring and continuing throughout the season.