Ah, the Diawl Bach—one of those little killers that just works when nothing else will. You know, it’s not flashy, but man, it’s saved my bacon more times than I can count. Let me tell you how I like to tie and fish this thing.

First off, keep it skinny. I usually grab a skinny hook—size 16 or 18, nothing too fancy—and build it slim. Some folks go for a medium shank, but honestly, I find the shorter ones just seem to get more takes, especially in slower water. For the body, I’ll dub on some hare’s ear or synth stuff, nothing too thick. You want it tapered, like a natural nymph, not some chunky mess. Then I’ll rib it with fine wire—still figuring out the best ribbing material myself, but copper wire’s been decent. Gives it that segmented look without overdoing it.
Tail and legs? Just a few pheasant tail fibers, maybe a couple hackle tips if I’m feeling fancy. Less is more here. And yeah, you can slap a bead on there if you need to get down quick—I’ll admit, the bead-head version’s my go-to in faster currents. Once I tried this on a tricky stretch of the River Wye where the fish were hugging bottom, and the extra weight made all the difference.

What’s it mimic? Pretty much any small nymph, really. Midges, mayfly nymphs—you name it. I’ve had days where it out-fished a Pheasant Tail when mayflies were hatching, which still surprises me. Works best in clear water, though. Muddy it up, and you might as well switch to something with more punch.

Fishing it? Dead simple. Nymph it under an indicator if you’re lazy like me, or tight-line it if you’re feeling technical. Either way, keep it natural. Let it drift, maybe twitch it now and then, but don’t overwork it. I’ve caught everything from wild browns to stubborn grayling on this pattern—just one of those flies that’s stupidly reliable when the fish are picky.
Only downside? It’s so slim it can be a pain to tie on in low light. But hey, that’s what headlamps are for. Give it a shot next time the fish are ignoring your usual stuff—might just save your day.