pond weeds

I need some advice on pond weeds. Our largely spring-fed pond, built about 40 years ago, is about 3/4 surface acre and 15-17 feet deep in the middle. Edges slope so there are reeds & cattails, not such a problem as I guess they cannot grow in more than 3-4' depth. The problem is a weed which a Dept of Lands ranger called duckweed. I am not sure that is what it is since picture on the Web look a lot different. Our weed leaves are enormous to those I've seen in pictures.
This weed growth has really increased in the last 5 or 6 years as there is some drainage into the pond from higher up on the hill where people are building homes on 5 acres lots is probably from fertilizer use on lawns, etc. We cannot prevent this influx.
The weed leaves are 2 or so inches long, like a fat spear shape. Stems are vining and rooted in - they seem to reach clear to the bottom. There is a seed-head looking thing here and there on the stems, and is 2 or so inches long, narrow. The stems look for all the world like philodendron gone aquatic.
Strangely, the bass, frogs & other creatures in the pond are having a wonderful time and have no problem with this canopy of leaves.
My husband spent the last 2 days in a boat hand "weeding", hauling up miles of stems and weeds so we can set up a water line from the pond to our garden. We have to clear this or the leaves will clog the water line filter. It was discourage as he barely made a dent the stuff is so thick. He cleared a lot last year and of course, it grew right back.
Hopefully, you can see the pictures of it at Shutterfly link below: http://share.shutterfly.com/action/welcome?sid=0QaOWrFq2bMXGw&notag=1 Just click on view pictures, then choose slide show - no need for a password.
Does anyone know what this is and how to get rid of it, or at the least, reduce it so it doesn't choke the pond to death plus make it impossible for us to use our water line.
Thank,s Deb
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I don't know if that is duck weed or not, Deb, that that is not what was called duck weed here. What I was told is duck weed has a leaf about the size of a pencil eraser and is eaten by the goldfish as well as ducks. In fact, someone told me that folks turning their goldfish loose endangered the supply of food for the ducks. I didn't investigate it, but can say that what I have is definitely eaten by the goldfish.
Good luck with the plants and reclaiming your water.
Glenna
snipped-for-privacy@gmail.com writes:

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On Jul 2, 5:10 pm, snipped-for-privacy@pmug.org (Glenna Rose) wrote:

Thanks, Glenna. I have found out, via another group specifically for ponds that the plant is Potamogeton natans and can be destroyed by the grass carp. The ranger from Dept of Lands was incorrect. We will have to go thru a process with Fish and Game to get some of these special sterile fish which will eat the plants. They will have plenty to eat for a long time. deb
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