Fantastic Offer On Natural Water-clear Treatment That Lasts For A Whole Six Months For Less Than £12. Place Barley Straw Bales In Your Pond & As It Breaks Down & Decomposes It Produces A By-product Which Feeds On The Nitrates That Green Algae Relies On. The Algae Starves & Your Water Becomes Clear Again.safe For The Family & Petstotally Organicno-messno Measuringyour Medium Bale Of Barley Straw Is Contained In A Net So The Straw Is Kept Together For Less Mess.2 Medium Bales Are Perfect For A Pond Of 2000 Gallons/9000 Litres (13x 13x 2ft) For 6 Months- Perfect For Over The Spring & Summer Or Summer & Autumn.