Shrimp can be very effective for rainbow trout. You can go to the store and buy shrimp. The frozen shrimp will work, but unfrozen shrimp will work better. It’s fresher and the trout can tell. In some places, the shrimp was frozen and then they let it thaw out and they sell it, so it seems like it is fresh, but it isn’t as fresh. Getting fresh shrimp is extremely difficult because you won’t find many trout destinations near saltwater, so don’t stress out too much if you have to go with the frozen stuff.