From what I've read the minnows and goldfish are pretty good at eating mosquito larvae and other insects, but not so great on algae control. I think a few snails would take care of the algae pretty well. I read that some snails called "trapdoor snails" would be good because they don't reproduce as well as some of the others, so you won't have a trough filled with the darn things overnight! Plus, the survive in frozen ponds when other species won't so they should be fine in winter.
I might have to try this. Maybe 2 minnows and a few snails to start.