Grass carp are a spooky fish. You've got to see the fish and make a lucky perfect cast that doesn't send em running. I've regulated my attempts at these grassies to windless sunny sky -- any ripples on the water and I just can't see 'em. They don't root around like common carp so they're difficult to spot. Using my 4wt as delicately as I can. The only fly that's hooked grass-lips is still the pheasant tail nymph.