Sounds to me like an alum treatment is in order to tie up the nutrients in the bottom of the pond, or as TJ said a drain and dip.

http://www.marinebiochemists.com/phosarticle.html

Even if your copper based herbicides did work, you run the risk of sterilizing your pond using repeated applications with a build up of a heavy metal, which in this case is copper.



Last edited by Cecil Baird1; 05/12/10 09:40 PM.
If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.