"Jack Schmidling" wrote in message
...

We had been so plagued with duckweed on our small pond that we just
declared the war over and lost interest in the pond. By late Spring, it
was a sea of green and might as well have been filled with cement. Other
than frogs, we could see nothing in the way of life in the pond.

Now you're playing in my pond. Like you were told in rec.gardens, use koi or
goldfish, they eat duckweed with much gusto. With the caveat that koi also
like to rummage at the bottom of the pond in search of aquatic insects to
feed on, so they can make the pond muddy.

There are herbicides that can be used to control duckweed, some have a
relatively low residual.
http://www.interstateproducts.com/pd...eliminator.pdf
For example has a relatively minor residual, but is toxic to aquatic
insects. So it could disrupt the pond's ecosystem.