Some people worry that a backyard pond will be a source of mosquitoes. Pond owners often stock mosquito fish to reduce the likelihood that mosquitoes will use the pond to reproduce.

Mosquito fish are tiny, about an inch long or less. They don't lay eggs. They give birth to free-swimming young after a gestation of a bit less than a month. The young grow fast and begin reproducing in a few months. It doesn't take long for them to saturate their habitat.

Mosquito fish, Gambusia affinis, are a good choice for small ponds without fancy water-quality gear like aerators and filters. They can live in shallow, scummy, poor quality water.

As a test of their effectiveness, I stocked one of two identical ponds with mosquito fish last summer. The other I left fishless.

On Nov. 19, I hauled out about 5 gallons of water and bottom detritus from each pond. I strained the water through a piece of cloth and put the contents of each into white bowls so I could see the insects and other pond life.

Sure enough, the fishless pond had a population of mosquito larvae. I failed to find them in the pond with mosquito fish.

Besides the mosquito larvae, the fishless pond had midge larvae and Eristalis larvae. Eristalis is a fly larva that has a long tail like a breathing tube, which it extends to the surface as a snorkel.

The fishless pond also had frog tadpoles. Those were interesting. I wonder if the mosquito fish had prevented frogs from successfully reproducing in the pond by eating newly 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, especially sunfish 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 huge swarms of vicious mosquitoes?

Mosquitoes are often in backyards without water nearby. Until this year I never had mosquito fish and was never particularly bothered by mosquitoes. Having a mosquito fishless-pond may not make a noticeable difference.