I've had some mixed results with gills (large and small alike), I did pretty good with a Griffith's gnat in size 18 fished on top (dry). The little gills can get ahold of the size 18's fairly well.
If that doesn't work out then I go to a woolly worm or bugger in a medium color range -orange, blue or tan body palmered with brown and/or grizzly hackle. I fish these in about size 8 to 12, (wet) along the beds - stripped along about 3-6 inches and then let sit for 5 seconds, then strip again. If that seems too slow then I count 3 seconds on a few strips. I don't rush it unless the fish prefer it that way.
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There's almost nothin' wrong with the first lie, it's the weight of all the others holdin' it up that gets ya'! - Tim
Jesus still hangs out with fishermen.