I spent a couple years pursuing rainbows and cutts in stocked lakes/ponds in Colorado -- all of which are stocked hatchery fish.They are stocked as fingerlings and quickly take on the characteristics of wild fish. These hatchery fish proved to be suckers for attractor dry fly patterns -- either a Royal Coachman or red or yellow or orange Humpys. These patterns, in a #14 or #16 size on a 5X 9' tippet worked best after the water warmed up a bit. Feeding time was generally best in the morning from sunrise to about an hour out. After that, we would switch to olive green scuds (sinking nymph) and let them fall to the bottom and retrieve in quick short jerks -- serious strikes though so use a heavier tippet (4X) and hold on. We generally didn't bother trying to match the hatch as we had enough action on these attractor patterns. In the winter we would fish these same fish through the ice (likely not an option in your locale) using tiny ice flies tipped with wax worms under a small bobber and just hammer them. Have fun!