10X - By my recommendation the one acre would to start off with just 3 GC young ones and if a couple old ones were present then 2 new GC. Note many people that don't like my suggestions think I don't know anything.

Watch the plants density then in the 2nd or 3rd yr add the 3rd new GC. As I noted prior, it is much better to have some weeds present as habitat and FA control than a denuded pond that usually results in FA problems because GC basically do not eat FA. Also when all the weeds are gone the GC resort to becoming pellet hogs and rooting in the bottom for invertebrates. The kill shot of the GC I noted above was taken out with a 12 gauge. For close range use, one does not have to be real accurate with a shotgun. . Borrow a shotgun or rent one from a pawn shop if you don't have one is my suggestion.