This a matchup between two proven subsurface patterns that trout really seem to love.
No, it’s not cheating or even unethical to tie a San Juan Worm to your tippet— worms are an important part of a trout’s diet, and if you’re not fishing because you think it’s on par with bait fishing, you’re missing out.
Named for the epic worm “hatch” in the San Juan River in New Mexico (anglers in the river have been known to do the “San Juan shuffle,” and kick up bugs and worms under their feet in order to get fish directly downstream to eat), the San Juan Worm has a loyal following, and it’s a great spring pattern, when high water causes erosion along the banks and puts actual worms in the river.
The Pheasant-tail Nymph is equally effective and is likely a more traditional choice for nymphing anglers. Using pheasant tail fibers both for the tail and for the wraps up the hook shank, this fly is one of the first patterns new tiers learn to tackle at the vise.
It’s also an excellent mayfly nymph attractor, and in larger sizes, it’s a reasonable representation of a stonefly. I love to tie and fish this pattern—it’s a winner here on my local waters in eastern Idaho, particularly in pre-run-off conditions on the Henry’s Fork and in the Big Wood River below Sun Valley.