If there was a vote on the most productive "small nymph" pattern for trout, it is likely the winner would be a Copper John pattern. It is a deadly fly on any water and a must have in your fly box. Carry lots and make sure to get the size range from top to bottom without too many holes in it. There are times when our guides can only catch fish on one size, one color. Black Red, Copper, Chartreuse... make sure to have them all and experiment with various colors if the fishing is slow. Sometimes the lighting is such that a certain color will make them snap! Bring a big net and a camera. Nice Rainbow Taken on a #16 Black Copper John Nymph!
Nymphs in rivers are successfully fished on a slack line drift using a strike indicator. This is because nearly all river nymphs either cling to rocks or crawl, very few actually swim. Wade fisherman will typically cast them upstream and let them drift downstream using mends to keep the line slack and the fly fishing "drag free" with no tension. Another method is using a dry dropper method. This is where you use your dry fly as the strike indicator and tie the nymph on underneath it, we have a killer video on this too! Dry Fly and Dropper Nymph Video "High Stick Nymphing Tips" and high stick nymphing is also done with a strike indicator and is deadly on big rivers where fast currents suck your line underwater! Some of the biggest trout live in water that has whirlpools and harsh seam lines. Learn how to high stick nymph by raising your rod up high and preventing drag from occurring when the line is sucked underwater. This is very effective, especially with rods longer than 9'.