That is where the the guy at the fish hatchery was coming from when he suggested 20 grass carp. He had a 1/2 acre that had a lot of duckweed and he put 10 grass carp in. It sounds like he was expecting almost instant results and when he didn't see it, he added another 10. The duckweed disappeared. My problem with his suggestion is that now he has 20 grass carp in a 1/2 acre pond that he will have trouble removing and there probably isn't enough plant life left in the pond. That is why I plan on trying only 5.
