Interpet Sludge Buster contains cultures of biological organisms which actively consume organic sludge and so takes the hard work out of keeping your pond clean and healthy. Each sachet contains 8,500 million bacteria to consume the pond sludge. Use pond sludge buster whether you have a filter or not. Use once a fortnight to achieve and maintain low waste levels. Use after using effective algae products (i.e. Pond Balance or Green Away) to consume the dead algae. Each sachet treats 500 gallons. 4 Pack will treat 2000 gallons, 20 pack will treat 10000 gallons. treat 10000 gallons.