Try rice fish. Most garden centers carry them for about $1 each.
Literally uncaring of water conditions. Uncaring of temperature. They even thrive in 106 degree stagnant water.
And they are mosquito eating machines.
Many states or counties have a mosquito abatement or vector control department. Many of these will give away Mosquito Eaters. These are a fish that looks a lot like a Guppy, but are more aggressive, and more adapted to a wider range of conditions.