Some people worry that a backyard pond will be a source of mosquitoes. Pond ownersoften stock mosquito fish to reduce the likelihood that mosquitoes will use the pond toreproduce.Mosquito fish are tiny, about an inch long or less. They don’t lay eggs. They givebirth to free-swimming young after a gestation of a bit less than a month. The young growfast and begin reproducing in a few months. It doesn’t take long for them to saturatetheir habitat.Mosquito fish, Gambusia affinis, are a good choice for small ponds without fancywater-quality gear like aerators and filters. They can live in shallow, scummy, poorquality water.As a test of their effectiveness, I stocked one of two identical ponds with mosquitofish last summer. The other I left fishless.On Nov. 19, I hauled out about 5 gallons of water and bottom detritus from each pond. Istrained the water through a piece of cloth and put the contents of each into white bowlsso I could see the insects and other pond life.Sure enough, the fishless pond had a population of mosquito larvae. I failed to findthem in the pond with mosquito fish.Besides the mosquito larvae, the fishless pond had midge larvae and Eristalislarvae. Eristalis is a fly larva that has a long tail like a breathing tube, whichit extends to the surface as a snorkel.The fishless pond also had frog tadpoles. Those were interesting. I wonder if themosquito fish had prevented frogs from successfully reproducing in the pond by eatingnewly hatched tadpoles. Next summer I’ll have to check that out.The bottom line is that mosquito fish can keep a pond free of mosquitos.Can other fish do as well? Yes, many kinds of fish eat mosquito larvae, especiallysunfish of various kinds. These fish will need a higher standard of water quality,however. Many predacious fish will eat mosquito fish along with mosquitos.Will ponds without mosquito fish make life unbearable for you by giving rise to hugeswarms of vicious mosquitoes?Mosquitoes are often in backyards without water nearby. Until this year I never hadmosquito fish and was never particularly bothered by mosquitoes. Having a mosquitofishless-pond may not make a noticeable difference.