Mark C.,
I'm no pond expert by any stretch but I'll toss this out to give you something else to consider. There have been some past conversations about the benefits of a drawn down when it comes to weed control. Given your location in Erie, Pa., and the cold winter months just over the hill, perhaps this is another avenue you could look into to help with weed control. Like Bill Cody said, check the other "weed control" posts.
Russ
