The Guppy Project to Help Stop Zika

Silver-spotted guppies fish with yellow and orange scales

The Spruce / Adrienne Legault

In the spring and summer, there is a threat that mosquitoes carrying the Zika virus may bite a family member and infect them. The Zika virus is carried by the Aedes species of mosquito and if you have a garden pond, adding guppies may help to stop it's spread

How the Zika Virus Is Spread

One way the Zika virus is spread is by the bite of the Aedes mosquitoes, which can breed in a pool of water as small as a bottle cap and usually bite during the day. The aggressive yellow fever mosquito, Aedes aegypti, has spread most Zika cases. That mosquito is common in most of the tropical world, and in the United States it is found in Florida, along the Gulf Coast, and in Hawaii―although in hot weather it has been found as far north as Washington, D.C.

Asian Tiger Mosquito

The much more aggressive Asian Tiger Mosquito (which is prevalent worldwide and is found in Florida’s Everglades), Aedes albopictus, is also known to be a prime transmitter of the Zika virus, but it is not clear how efficiently yet. That mosquito ranges as far north as New York and Chicago in the summer. This is the mosquito most likely to bite at pool parties, outings or on the patio day or night. 

Guppies Can Prevent the Zika Virus Spread

The spread of the Zika virus throughout the world is growing. The mosquito will be the main transmission of Zika, and the guppy can be the easiest and cheapest preventative precaution against the Zika virus if you have a pond in your backyard.

Mosquitos are now more dangerous than ever, as Zika virus spreaders. Mosquitoes reproduce by means of laying eggs on standing water, which produce aquatic larvae, maturing into adult Mosquitoes very quickly. If there is a still body of water, any water, they will breed in it!

Guppies (Poecilia reticulata), in spite of their tiny size, are useful inhabitants of ponds they have been introduced into and inhabit. Specifically, one of their favorite foods is mosquito larvae and mosquito eggs. This tropical fish, the Guppy, is able to eat almost their total weight of mosquito larvae every day! 

Whether you have a goldfish pond or just a water garden in your backyard this summer, you need Guppies. If you have an old pond you have forgotten full of standing water, you need Guppies!

Guppies are very prolific; they are known in the West Indies as “million fish” for a very good reason. If you put 5 or 6 females and a few males in a body of water at the beginning of the warm season (water temperature at least 65 F), within 6 months, under ideal conditions it is possible to have thousands of Guppies, it will seem like millions of the little mosquito eating gems. 

Mosquito Control

The sum total of their efforts in mosquito control made much of Florida inhabitable in the 19th century, as well as many other areas of the world. The extent of their contribution is debated but they seem as desirable in nature as they are in the aquarium. Yes, the ​guppy is an invasive species in almost every corner of the world, but one that has worked out well in almost every instance.

Their undeniable contributions to verified mosquito control and prevention of the diseases carried by mosquitos and their bites have continued to this day. One recent example of the guppy saving human lives from disease was in Mangalore, India:

The Guppy, a freshwater fish popularly kept in aquariums, eats mosquito larvae and eggs and thus helps reduce the spread of malaria as the disease is caused by the parasite Plasmodium, which is transmitted to humans through mosquito bites. As a means to control mosquitoes, the guppies are left in stagnant water puddles where mosquitoes breed. The fish then eat the mosquito eggs and larvae, leading to reduced mosquito population.
Nripendra Kumar Sarma from the public health engineering department said that bio-control helped Assam significantly reduce its malaria cases. "Till 2012, we had over 30,000 cases each year. But now they are no more than 3,000-4,000 in areas where the Guppies were introduced. This approach can very well be initiated in areas (of the country) that are prone to malaria, dengue and Zika, all of which are mosquito-borne diseases," Nripendra Kumar Sarma said.

Mosquito Free Ponds and Standing Water Pools

If you have goldfish in the pond, they will not hurt the guppies in any way, they won’t even notice them. But remember goldfish will not eat mosquito larva or their eggs. When the weather gets warmer and the water temperature gets over 60 F, go to your local pet store and get 3 to 5 very pregnant female guppies. You know they are pregnant by a large black gravid spot on the back underside of her belly, and a very fat “squared off” belly.

If you want to get a few males, they are pretty, but you actually do not need them, and here are 3 good reasons why males are not critical to this equation:

  1.  Once a female is impregnated she can have up to 6 broods of up to 80 fry (baby guppies) without being inseminated again. When the male inseminates the female, he deposits a “packet” of sperm, this “packet" will re-impregnate her over and over. In nature, guppies live on flood plains and get flushed from puddle to puddle, they may never see a male again, and they really don’t need to.
  2. The females are the ravenous eaters, the ones that can eat almost their weight in mosquitoes each day, they are eating for 80 after all, the males are much smaller and actually lazy, and they have one purpose, you know what.
  3. When a guppy is born outside in a pond, with virtually unlimited food, they can be sexually mature in 3 to 4 weeks. So mom won’t be lonely long, this is also why it is said guppies are almost born pregnant. They do not mature this fast in an aquarium because of space, food, and nature.

Do not worry about feeding Guppy’s outside, they will find a way, just leave them alone and be surprised.

For added fun, get pregnant fancy guppy females, by the end of the summer, you will have a riot of color and a nice group to take into your home aquarium if you like.

  • Any fish grown in an outdoor pond will be healthier, larger and more colorful than a fish you may buy in a store. But also remember that the fish you buy in a store were themselves most likely raised in a pond, on a fish farm, but not allowed to mature in the pond, they were taken out while still small to better acclimate to the store where you bought them and then your aquarium. You will find some real surprises at the end of the summer; if you follow the simple guidelines we have set out here, and just let nature take its course. In the process, you will be keeping your family safe from Mosquitoes and end up with a great lesson in the nature of fish. 
  • Goldfish are grazers, they will not eat mosquito larva, and the Zika virus is no joke. Wherever you are in the world, get some guppies and put them in whatever pond water you have in your backyard. Chemicals are bad for you, bad for wildlife and bad for the environment. The guppy solution is cheap, clean and totally environmentally friendly!
  • Guppies are tropical fish and will not survive cold water, so if the temperature drops below 65 degrees Fahrenheit in the fall or winter, the guppies will need to be brought inside until the water warms again in the spring. Mosquitoes are also inactive in cold weather, so there is less risk of them at this time.

There is concern about introducing nonnative species, such as the Guppy, into natural bodies of water (lakes and rivers) but this is appropriate for use in pools or ponds in back yards. Do not release Guppies or other nonnative tropical fish into the wild waters without first checking with local government wildlife officials.

The Mosquito fish (Gambusia affinis), similar to the Guppy, has been introduced by the government officials into areas for mosquito control. It will survive cold water through the winter and so does not need to be brought indoors, like the Guppy does. Many Koi dealers sell Mosquito fish to add to koi ponds for mosquito control.