Yes - minnows eat mosquito larvae. Actually, they are supposed to do a better job than mosquito fish.
That is why I got interested in them in the first place. I was looking for gambusia, but then read up on them a bit more and found that they tend to favor other insects and fry more than mosquitoes. Minnows tend to be less aggressive, are brighter colored, school nicely near the top, and like to each mosquitoes.