Treats flukes and worms. Stops fish flicking / itching. Can be used to sterilise new plants before introducing them to your pond. Safe with fish plants and filtration bacteria. For use in garden ponds. 250ml / 5 day course for 3600 litres 500ml / 5 day course for 7200 litres 1 litre / 5 day course for 14000 litres.