For crystal clear water & a healthy pond, add pure pond to your filter once a month to help remove ammonia & nitrite. Use pure pond when starting up a new filter & whenever an improvement in pond water clarity is required. Pure pond contains millions of live bacteria & can be added to most pond filters, use a filter bag to prevent escape into the pond if necessary. 500ml of pure pond is ideal for ponds up to 10,000 litres. 1 litre of pure pond is ideal for ponds up to 20,000 litres. 2 litres of pure pond is ideal for ponds up to 40,000 litres.