On Fri, 18 Jan 2008 10:49:07 CST, Chris Barnes
wrote:

Galen Hekhuis wrote:
Just as a data point, I'm up in northern Florida and my experience has
been that duckweed can entirely take over a pond.

I know it can completely take over a small pond. But since I have never
seen it take over, say a lake (I have seen it in lakes, but it's always
confined to small coves or along the edges).

Therefore, I presume that there is some limit to how big of an area it
can take over. Maybe it's fish eating it (most fish aren't veggies)?
Maybe it's the wind blowing it to one end or the other?

*IF* there is a limit, then where is that limit? Ie. is the pond I
described big enough?

I don't really know, my back pond is about the size you describe, but
only about 5 1/2 feet deep. When I first moved here it was pretty
clear, then in the space of about a month it became completely
covered. Personally, I think the alligator ate the critters that
were keeping it clear, but I don't know for sure and I can't even say
for sure that there were critters keeping it clear. My middle pond
is some 50 -60 thousand gallons when it has water in it, which the
current drought has made rather difficult. Even though it is visited
by waterfowl, and has been visibly "seeded" with live duckweed plants,
none of it has ever taken hold and the pond remains duckweed free. The
front pond is about 40 feet by 120 feet, and has always been covered
with duckweed, as far as I know.

I stuck an aerator in the middle pond which may deter the duckweed. I
can get power to the middle pond, the others are over 1/8 mile from
power, and I don't have an extension cord long enough to try in the
others. I did try a little solar power aerator in the back pond
with mixed results. It was far, far too small for the pond, but it
managed to keep a little area (about silver dollar sized) open.
Unfortunately, they want more bucks for a large sized aerator than I
am willing to spend on an experiment.