How to Prevent Mosquito Breeding in Cisterns

Mosquitoes are a familiar flying nuisance, and they need still water to lay their eggs.

Mosquitoes place eggs in still water. such as found in a cistern.Mosquitoes place eggs in still water. such as found in a cistern.
Since many species also carry disease, preventing standing water for them to use can drastically reduce this risk around the home. Landscape cisterns, used to hold rainwater for property use, can offer the ideal breeding place for mosquitoes. There are several steps that can be taken to prevent the cistern from becoming a mosquito breeding tank.

Change or use the water in the cistern once a week. Be sure the container is empty and completely dry. Mosquito eggs and larvae can survive in tiny amounts of water.

Use a tight-fitting cover to prevent the mosquitoes from gaining access to the water. Add a small amount of cooking oil to cover the water surface if the lid is not tight, was left off, or if mosquitoes have found a way in.

Add the bacillus known as Bt to the water. This bacteria is harmless to animals. Follow the product label instructions for application rates.

Keep mosquito fish in the cistern if you are familiar with keeping fish as pets. These fish eat mosquito larvae, but will need care and proper water parameters. Fish are the most complicated method of mosquito prevention.

Things You Will Need

  • Bt (Bacillus thuringiensis)
  • Cistern cover
  • Cooking oil
  • Mosquito fish

Tip

  • Cooking oil suffocates the larvae, but leaves the cistern water safe for landscape use.

Warnings

  • Be sure to float a board or other object to prevent animals, small children and birds from drowning in the cistern.
  • Do not add fish to the cistern unless you want to keep them as pets and the cistern is very large -- over 50 gallons and deeper than 30 inches for a few mosquito fish. Only experienced fish keepers should maintain this type of cistern.