Take care to make sure you are getting your presentation down to the fish. The first few hours I fished the canal, I was getting nothing on the fly even after changing up through different sizes and colours. This was using a full floating line and a slow sink tip. It was only until i put a full sink tip on (6 ips) that I caught fish and a lot of them. Previously i was not getting down enough, even though the water looked fairly slow.
Care was needed to balance depth to prevent dredging the bottom and snagging fish, but once you get the right combination of sink rate, casting at different angles across the flow and strip rate you should be able to get into them. Fly in my experience usually outperforms gear. Also try chartreuse. They tend to be more interested early morning and evening once the sun is off the water.