You could also try a betta. They tolerate high temperatures, and their natural food is mosquito larvae. And, if you get one with light or irridescent fins, they are just GORGEOUS when they swim just below the surface.
ONE male per pond, or they'll kill one another. A male and female will breed, but you have to remove the female afterwards (the male keeps the eggs) or have enough space and shelter that she can hide until it's time to mate again.
I rotate my bettas from the house to my tub ponds outside, for a day or two at a time, to eat mosquito larvae. Or I scoop the larvae and divide them up between the jars of fish in the house.
They're about $3 at PetSmart.