GB,
I see your point about the Reward but there are many situations where its the only option so I would discount it all together. sonar or avast will eradicate duckweed but if there is a good sized stream feeding the pond those products will not work. Reward is excellent at killing duckweed, it rarley eradicates the problem but I have eradicated duckweed with Reward. 95% of the time you need to look at Reward treatment on duckweed like mowing the grass, it has to be done often to keep it in check.
