Faster action than conventional barley straw. An eco-friendly product for the treatment of algae and blanketweed. It enhances the natural water chemistry, leaving pond water clean and clear. the contains no synthtic chemicals or artificial pesticides. It is harmless to all other aquatic plants and wildlife. Suitable for use in all types of pond. 250ml - treats 4,500ltrs (1,000 gal) 500ml - treats 9,000ltrs (2000gals)