I had coontail in my lake and it grew to the surface from as deep as 11 feet when my lake was at its worst. We put a bunch of grass carp in as the others from long ago had gotten huge, old, and many appeared to have died off. The carp didn't phase the coontail and the hatchery I got them from told me just as much but I wanted to at least give it a try anyways.

We ended up hiring an excavator to cut our dam open last year and then doze out the muck this summer. We also had all the trees and willows torn out from around the banks. Our lake is close to three acres and the man we hired happened to be the same guy who built it 40 years ago. I know that is an expensive alternative but so are weed killing treatments once your water gets overtaken in a big way. He did us pretty good though. Our final tally was a little over 10k but I imagine we could have been billed 20 to 30k from others.