Waterlife Sterazin P is used to control both body and gill flukes in pond fish. Flukes are invisible to the naked eye but cause fish to \"flick\" and \"scratch\". Flukes are normally the correct diagnosis when fish are demonstrating this behaviour and no other symptoms are present.Sterazin P should be used on days 1 3 6 8 and 10 in order to catch the parasites in all stages of their life cycle. Sterazin P is safe even with sensitive fish such as Orfe and Rudd but should not be used with Sturgeon and Sterlets.In addition Sterazin P\'s fish health properties can be used to aid the sterilisation of new plants when introduced to your pond. Plants should be bathed in a clean container and left in solution for 2 hours. 125ml bottle - 5 day course of treatment for 1800 litres. Also available in 500ml bottle.