HSE approved algaecide for blanketweed. (HSE7695) Independentently proven to suppress blanketweed Directly suppresses blanketweed and other filamentous algae. Easy-to-use, harmless to fish, plants and wildlife Application Add 50ml of AlgoFin for every 1000 litres (220 gallons) of pond water. Shake the bottle well before use. Add a half dose every 4 to 6 weeks for long-term suppression . Always read the instructions carefully before use.