I have caught all the carp in my life on nightcrawlers fishing for other species. However corn and fermented dough baits probably work better. For grass carp, cherry tomatoes, lettuce, and aquatic plants are the best baits. I have seen some of these grassies approach 5 feet in length and I bet they would be almost impossible to land. A guy fishing for bluegills with his flyrod in waters where grass carp occur told me that he had broken two fly rods in one summer when a grass carp thought his foam spider looked tasty.