as 1minute suggested midges and light tippet and long leaders.
I have good luck with zebra midge in 20 to 22, on top griffith's gnat in 20.
I tie up a soft hackle zebra midge in 18 -22 and will cast quartering down stream and swing it. Explosive strikes
Serendipity in 20 22 too works,
I have found fast rods using small flies and light tippet equals a lot of break offs especially in the hook set. I use a soft rod for winter fishing.
Another successful method is to throw big streamers and sink tips and swing them into deep holes, under cuts, logs for big fish. I stack my line to gain depth
oh as pugs mentioned get tiny black stone fly hatch too
