My 2 cents from experience. Copper products will not rid the pond of pondweed. It will turn brown and wither but will come back from the roots.

Cutrine Plus, K-Tea, Captain, and Clearigate are all chelated or compound copper herbicides and can be used in a mixture with Reward or Aquathol K. Other chelated or compound copper formulations are available but are not linked to this web site. - Aquaplant

Look here for herbicide labels which have the info.

http://plants.ifas.ufl.edu/guide/labmsds.html#imazapyr