Im fishing still waters around the northeast and have become very frustrated because I can't match the very small flies the trout are feeding on. I've flies down to size 18 but Im unsure how to fish them, line size must play a big part ? It seems trout will not take anything ( I've been though the box) once they are feeding on these tiny flies any help would be great.

The flies may be caenis -and once the Trout become preoccupied they do present a challenge. Even a sparse hackle on a 20/22 hook is too big!

So go to the other extreme, if allowed, large flashy streamer type pulled back very quickly through the feeding area.

Idea being your streamer fly becomes competition for the smaller fly and is attacked by the Trout......

Has worked for me in the past.

Len

Right............ Thanks for that will give it a try Checked caenis on google thats what I have spooned from trout in the past so I now know what there called. This is the pic I found, these must be hatching onto the surface.