No I would not recommend grass carp. In 1 acre pond stocked 3 in 2000 plus 10 more in 2003. In 5 acre pond stocked 15 in 2000 plus 50 more in 2003. The initial stocking did little to controll weeds. The latter stocking did have some effect on weed controll. As the grass carp age and grow bigger, their weed control ability greatly decreases. The grass carp grow fast and large, most of mine are in the 20# plus range. That is a lot of biomass for a fish that is extremely hard to catch. If you have any flowing water out of your pond, that is not gated, they will escape. In my experience you get about two years of semi weed controll then you have years of useless biomass in your pond. They are also hogs at the protein feeders.
