Poecilia reticulata

The Guppy, also known as the “millionfish,” is one of the most popular freshwater aquarium fish in the world. It is native to eastern South America (Venezuela Guyana, Brazil) and several adjacent island groups (Barbados, Netherlands Antilles, Trinidad and Tobago, the US Virgin Islands). Wild fish generally are found in small streams and ponds but can tolerate a range of water conditions.

The pet trade features a wide variety of guppies. The plain-looking "wild" guppy is very hardy and breeds quickly in captivity. Selective breeding by aquarists has also created "fancy” guppies. These are highly variable in appearance, featuring a range of bright colors and graceful fan-like or spiked tails.

Did You Know?

The Guppy, also known as the millionfish, is one of the most popular freshwater aquarium fish in the world.


Does the harvest for wildlife trade or captive breeding of this species harm wild populations?

Little Cause for Concern

Guppy populations appear to be thriving in their native range. Guppies will often use deteriorated habitats in rivers where few other species can occur.

EcoHealthy Recommendation:

Only acquire a pet that is from a reputable breeder or dealer to ensure that you are not buying an illegally wild-caught and/or imported animal.

Invasion Threat

Does the release or escape of this species into the wild harm the environment and/or economy?

Significant Cause for Concern

Guppies have successfully established wild populations in at least 32 countries in the Americas, Europe, Asia, Australasia, and Africa. Some introductions have been accidental but there has also been deliberate release for mosquito control (guppies eat mosquito larvae). In some locations these introductions have been harmful to native fishes; in others, no impact has been recorded.

EcoHealthy Recommendation:

Before obtaining any non-traditional pet, check that it is legal to own one in your state of residence and check for permitting requirements. Only acquire a pet that is from a reputable breeder or dealer to ensure that you are not buying an illegally imported or wild-caught animal. Always keep your pet inside a safe and secure enclosure. Never release a pet into the wild.

Ease of Care

Does harvest, captive breeding, transport, or being kept as a pet harm individual animals?

Some Cause for Concern

Ease of care of many non-traditional pets depends on the individual owner’s years of experience and knowledge caring for a particular species. For the purposes of this website, we have geared information toward the benefit of the beginner.

Guppies require appropriate salinity range (they prefer slightly brackish water), water quality, pH level and temperature. It is recommended any live offspring be kept in a separate tank.

EcoHealthy Recommendation:

Before acquiring a guppy, be sure to research its specific care requirements. Ask about the general health of the group of guppies from which you are purchasing your fish.

Health Threat

Does this animal pose a health risk to native wildlife, humans, livestock and agriculture?

Some Cause for Concern

Guppies are known to carry various parasites and pathogens. In particular guppies are known to harbor Mycobacteria that can cause disease in fish and skin infections in humans. Guppies may be carriers of these bacteria even if they appear to be healthy. People with compromised immune systems are susceptible to these skin infections, commonly known as “fish-handler’s disease.”

EcoHealthy Recommendation:

Due to the potential for disease transmission to humans and other household pets, always wash your hands after handling a fish or touching the aquarium water. When purchasing a pet fish ask the seller if the fish or group of fish has a history of any health problems and for a list of any medical treatments the animal or tank has received.

EcoHealth Alliance works at the intersection of ecosystem, animal and human health through local conservation programs and develops global health solutions to emerging diseases.
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