Duckweed control is a frog friendly Duck weed treatmentDuckweed Control contains a specialist bacterial culture which removes nutrients key to the growth of the most common species of duckweed (lemna minor) so that once existing weed has been removed its return is inhibited.Duckweed Control will not harm fish,wildlife or other plantlife in the pond.1000ml treats ponds up to 9000 Ltrs.Initial Dose: One full measure from dosage chamber per 450 litresMaintenance: 10ml per 450 litres weekly