I have three ponds also. The front one and the back one are covered
in duckweed, but the middle pond (near the house) doesn't have a bit.
I know it has been "inoculated," I've seen ducks, cormorants, ibises,
egrets, and others visit the pond. I've even seen duckweed floating
in the pond, but I guess it just dies out because the pond stays free
of it.

I've been a cave explorer for some 40+ years and now live in some of
the best cave diving country in the world (northern Florida). Having
spent so much time underground and having friends that actually swim
around in the underground water I am extremely anal about putting any
kind of chemical where it can get in the ground or groundwater.
Herbicides are right out for me. I have no fish in the pond, either.
I haven't the foggiest why I don't have any duckweed there.

I've tried to search for solutions but haven't found hardly anything
promising. Methods of biological control (mainly fish that eat
duckweed) have mixed reviews, the majority seem to think it a pretty
iffy proposition, if not an outright poor method of control.
Mechanical methods (skimming and the like) seem to provide only very
temporary fixes. That leaves chemical methods (herbicides), and aside
from my reluctance to go that route it isn't a cheap way to go,
either. Besides, just about anything that kills duckweed kills a lot
of other stuff too, there doesn't seem to be anything like a duckweed
specific herbicide.

On Sat, 23 Jun 2007 15:51:32 CST, Galen Hekhuis
wrote:

I have three ponds also. The front one and the back one are covered
in duckweed, but the middle pond (near the house) doesn't have a bit.
I know it has been "inoculated," I've seen ducks, cormorants, ibises,
egrets, and others visit the pond. I've even seen duckweed floating
in the pond, but I guess it just dies out because the pond stays free
of it.

I've been a cave explorer for some 40+ years and now live in some of
the best cave diving country in the world (northern Florida). Having
spent so much time underground and having friends that actually swim
around in the underground water I am extremely anal about putting any
kind of chemical where it can get in the ground or groundwater.
Herbicides are right out for me. I have no fish in the pond, either.
I haven't the foggiest why I don't have any duckweed there.

I've tried to search for solutions but haven't found hardly anything
promising. Methods of biological control (mainly fish that eat
duckweed) have mixed reviews, the majority seem to think it a pretty
iffy proposition, if not an outright poor method of control.
Mechanical methods (skimming and the like) seem to provide only very
temporary fixes. That leaves chemical methods (herbicides), and aside
from my reluctance to go that route it isn't a cheap way to go,
either. Besides, just about anything that kills duckweed kills a lot
of other stuff too, there doesn't seem to be anything like a duckweed
specific herbicide.

Maybe it is just my fish. But my little inside pond was covered with it
after over wintering the tropicals. I was thinking what a job it was going
to be to net it out so I could clean the muck on the pond. Then I purchased
4 small wakins. The only duckweed in there now is what washed up on two
fake lilies where the fish can't get to it. I was able to vac the bottom
out a few days ago. :-)

My Q-tank is another place it disappears with relish. Probably because
there isn't much else to eat, other than the food I throw in. IMHO, if the
fish aren't fed, they'll eat the duckweed. But in a natural pond, there is
a whole lot of other things to eat.... YMMV. ~ jan
------------
Zone 7a, SE Washington State
Ponds: www.jjspond.us

"Galen Hekhuis" wrote in message
...
Besides, just about anything that kills duckweed kills a lot
of other stuff too, there doesn't seem to be anything like a duckweed
specific herbicide.

Brevity snips....
========================
I'm having problem growing it this summer for some reason. It turns beige
and dies. I have several tubs I grow it in for the fish, as treats.
Usually it grows as fast as I harvest it,... not this year. :-(
--

RM....
Frugal ponding since 1995.
rec.ponder since late 1996.
My Pond & Aquarium Pages:
http://tinyurl.com/9do58
Zone 6. Middle TN USA
~~~~ }((((* ~~~ }{{{{(ö

Well, I was out this morning looking things over after at really NICE
t-storm that swept through the Springs last night. And what do I
behold growing next to some snapdragons that have decided living in
the bio-mech filter media (scrubber pads) is preferable to living in
the soil of the berm. And they are flourishing too! But anyway,
right next to this particularly healthy bunch of snap dragons I seen a
few bits of duckweed! My duck weed has been dead for months and
NOTHING was growing in the veggie filter and bio-mech filters that I
did not put there (except the snap dragons). Healthy looking duck
weed too! So, transfered some to the veggie filter and we will see
what happens. I put about 5 little duckweed plants (that is about all
that was in the other filter so far) in the veggie filter. Will let
you know how it grows!
Happy ponding!
W Dale

My friend Marilyn Buscher, the Pond Lady
(http://home.wi.rr.com/windyoaks/), has these big greenhouses over
shallow water for cultivating water plants. duckweed uses up the
nutrients AND shades the water and is not good for business. She
basically rigged up something a lot like a pond skimmer to remove the
duckweed. It works, it keeps the weed and azolla off her ponds.
Ingrid