Grass carp do not breed/reproduce in lakes or ponds even if they are fertile diploid fish. I am not aware of any state that allows the use of fertile diploid fish. The grass carp being stocked must be triploid infertile fish so that if they wash out of the pond/lake they don't start reproducing in the wild and destroy the native vegetation.

Most grass carp are raised at fish farms are pellet trained, so you could utilize pellet immitations to catch them. I personally like bow fishing though.