On Fri, 14 Aug 2009 08:32:33 EDT, Jim Elbrecht
wrote:

Galen Hekhuis wrote:

As requested, here is what the pond looks two days after I threw in
the aerator from the bank.
http://i181.photobucket.com/albums/x...g122009004.jpg
I know it doesn't look like much, but I really don't expect anything
in a hurry. In the time lapse photos you can see the duckweed blanket
move back and forth, east and west, or left and right as you look at
the picture, some 8-9 times a day. In the background, it seems like
cracks may be beginning to form, but maybe it's just wishful thinking.

Is it discouraging it, or just compacting it? Have you asked
your local county agents [in NY I'd ask Envirnmental Conservation- and
Cooperative Extension folks- don't know what they're called in your
part of the world] for advice? My instinct is that a couple
sterile grass carp couldn't do any harm.

Cornell University, in NY, is always experimenting, so I give them a
call on lots of stuff. I googled for this one and found their pond
page.

http://pond.dnr.cornell.edu/Pond/Com...c.htm#duckweed
They suggest aeration and grass carp.g Guess we covered that.
[they also mention a rake- which I had thought of, but in a more
automated, giant vacuum type device that works when you're sleeping.]

From what I've read, it seems that there isn't anyone who has a real
answer. The general consensus of opinion is that grass carp eat
duckweed, the sterile variety would without doubt be the best in this
area, but grass carp are not that effective once the duckweed has
taken over. Mechanical control (rakes and the like) is much more
effective, but due to the rate at which duckweed grows, has to be done
rather frequently. My hope is to provide an environment where
duckweed just doesn't like to grow. The agitation of the water by the
bubbler may just do that. Plus, I already had an aerator in another
(duckweed free -- well, mostly water free too) pond. I don't have any
triploid grass carp. I just started with what I had on hand that
might work.