How do you get rid of pond weeds ?

Question:i have a 6 acre pond and it is full of weeds

Answers:
Copper sulphate crystals will control a lot of pond weeds by removing the oxygen from the water resulting in the death of the weeds. However you can only treat about 1/4 of the pond at a time because the fish and other life forms cant live in the water with no oxygen either. Reward is a herbicide that is also sprayed on weeds that are rooted into the bottom of the pond.Its would have been better to start earlier in the spring because its much more to treat now.