Choosing the right fly for lakes might seem confounding, but here are a couple of rules to stick to—consider these the “foundation” for choosing flies for stillwater reservoirs, lakes and ponds:
1) Most coldwater lakes that have trout also have small aquatic insects called chironomids. These bugs slowly work their way to the surface, and flies depicting their nymphs can be “drifted” in lakes at various depths. When nothing else is happening, it’s a near certainty that chironomids are in the water and are, indeed, happening.
2) Sillhouette matters. On clear days, trout will likely see stripped flies from the bottom. Flies that “swim” naturally or look like food will get the first look. Also, consider some contrast in the fly patterns, and don’t forget your color choice—use the old “rule of thumb,” dark skies, dark fly, light skies, light flies.”
Above, Russ Miller of Fishpond elaborates, and goes a bit further, noting that, on lakes, sometimes the best sources of food blow into the water from the land. This time of year, think grasshoppers and ants struggling in the surface film. Consider near-shore amphbians, like frogs and toads. A lot of anglers prefer moving water to fishing lakes (and I count myself among that crowd), but lakes force anglers to be a bit more creative … to think a little harder when it comes to what’s in the water and what fish are chasing.
— Chris Hunt