Chronomids with virtually no retrieve. Colors and sizes vary widely and the best way to know what to use is to look in the water. If they are there, you will see them.

For general patterns, things like Hare's Ears and Prince nymphs have caught a lot of fish and would allow for slightly more interaction than chronomids. Same thing for soft-hackle flies like Spiders and Carries (sp?).

I'd almost always rather fish with a floating line than a sinking.

All that said, hopefully some others will chime in with more honed info.

-AP