However much effort you put into removing duckweed its very likely that you'll miss some and it will grow again incredibly quickly. Duckweed 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 the majority of the existing weed has been removed its return is inhibited . Duckweed Control will not harm fish,wildlife or other plant life in the pond.