The Guppy's Evolution: From Pet To Pest

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Guppies are a popular choice for home aquariums due to their vibrant colours, peaceful nature, and ease of breeding. They are a small, pretty species of tropical freshwater fish, native to South America. However, they have now been introduced to every continent except Antarctica, and are considered an invasive species in many places, causing a decline in native fish populations.

Guppies are highly adaptable and can survive in a wide range of water environments, including temperatures from 64.4 to 82.4°F (18 to 28°C) and salinity of up to 150% seawater. They are also able to tolerate poor water quality to a certain extent, although this can lead to health issues and death.

In terms of diet, guppies are omnivores and will eat algae, invertebrates, insects, and debris from the water. They are also known to prey on the eggs and larvae of other fish species.

Guppies typically live for around two to three years, both in the wild and in captivity.


Guppies as an invasive species

Guppies (Poecilia reticulata) are a species of small tropical freshwater fish native to certain countries and islands in South America, including Trinidad and Tobago, Venezuela, and Guyana. They are sexually dimorphic, with males being brightly coloured and patterned, and females a solid silver colour. Guppies are also highly adaptive, able to survive in a wide range of water environments, including heavily polluted bodies of water.

Guppies have become an invasive species on nearly every continent except Antarctica, and have been implicated in the decline of native fish populations. They were introduced to Hawaii through fish farms or aquarium release and have been established there since 1922. In the US, they have been found in many states, most likely due to aquarium or fish farm releases, and are considered established in Hawaii, Idaho, New Mexico, Nevada, Texas, and Wyoming. Guppies have also been found in Puerto Rico, the Virgin Islands, and Guam.

Guppies are considered dangerous as an invasive species because they carry several diseases and parasites that can damage local populations. They are also known to eat the eggs of native fish species, contributing to population decline. Guppies have been observed to take advantage of the presence of native species to reduce their refuge emergence latency and acquire information. They have a strong tendency to associate with native Goodeids, which helps them locate food faster and acquire information on food availability.


Guppy breeding

Guppies are easy to breed and care for, making them a great choice for beginners and experienced fishkeepers alike. Here is a guide to help you get started with guppy breeding:

Tank Setup and Supplies:

  • Tank size: A 10-gallon (37.85-liter) tank is a good starting point, but larger tanks (e.g., 25-liter/5.5-gallon or 36-45 liter/8-10 gallon) can accommodate more guppies and provide room for growth.
  • Filtration: Use a sponge filter or an air-driven corner filter to prevent fry from being sucked up. Ensure adequate airflow—the water above the filter should look like it is boiling.
  • Substrate: Substrate is optional and can be bare-bottomed for easier cleaning. If using substrate, consider gravel and crushed shell to help maintain water quality.
  • Plants and Decorations: Provide plenty of hiding places for fry and females. Use live, plastic, or silk plants, as well as wood, rocks, and other decorations. Floating plants like water lettuce and coontail are recommended.
  • Lighting: A light is optional but recommended to provide a sense of day and brighten the tank. Ensure your tank is cycled before adding fish.
  • Temperature: Maintain a temperature of 72-82°F (22-28°C) for adults and 78°F (25.5°C) for fry.
  • Water Parameters: Ideal water conditions include a pH of 7.2 (normal range 6.8-7.8), 8-12 degrees GH (normal range 4-20 degrees GH), and regular water changes of 25% weekly.

Selecting Guppies for Breeding:

  • Male-to-Female Ratio: Aim for a ratio of one male to two or three females (1:2-3) to reduce stress on females. In a 10-gallon tank, keep no more than 8-10 guppies, such as 2 males and 6 females or 1 male and 3 females.
  • Color and Tail Shape: Choose guppies with desired color patterns and tail shapes, as these traits will be passed on to the fry. Common color patterns include Wild, Albino, Blonde, and Blue, while tail shapes vary from rounded to sword-like.

Breeding Process:

  • Breeding Tank Setup: Prepare a separate breeding tank with hiding places for fry, such as low-floating plants and some high cover. Remove the substrate and use a gentle filter to protect the fry.
  • Feeding and Care: Provide high-quality food with increased nutritional value to promote healthy breeding. Feed guppies a variety of foods, including flakes, pellets, frozen bloodworms, and brine shrimp. Avoid overfeeding, and remove uneaten food after 5 minutes.
  • Pregnancy and Birth: Female guppies will develop a dark "gravid spot" and a squarish abdomen when pregnant. Guppies give birth to live fry, typically 20-60 at a time, after a gestation period of 21-31 days. Remove the female from the breeding tank immediately after giving birth to prevent cannibalism.

Caring for Fry:

  • Tank Conditions: Keep the fry in a clean tank at around 78°F (25.5°C). Perform frequent water changes (40% every few days) and siphon the tank to maintain water quality.
  • Feeding: Feed the fry brine shrimp, micro-worms, or powdered flakes twice a day. Ensure the food is crushed into small pieces suitable for their tiny mouths. Remove any uneaten food to prevent water contamination.
  • Health and Growth: Monitor the fry for any signs of illness or abnormal behavior. Remove any dead fry, and make necessary adjustments to water parameters or diet if issues arise. After about 3-4 months, the fry should be ready to join the community aquarium.


Guppy diet

Guppies are omnivores, meaning they eat both plants and animals. In the wild, guppies eat a variety of plant and animal matter, including algae and insect larvae. In a home aquarium, however, their diet is slightly different.

Guppies will eat almost anything you offer them, but it's important to ensure they stay healthy. Guppies can be overfed very easily as they always look hungry, so it's important to feed them a good diet and a variety of food.

Guppies should be fed once or twice a day, with a small amount of food that they can eat in 20-40 seconds. Guppies have tiny mouths, so it's important to ensure the food is small enough for them to eat.

There are many commercial foods available for guppies, including:

  • Flake food
  • Pellet food
  • Wet food (live and frozen)

Flake food is a common choice for guppy owners as it is inexpensive and dissolves quickly in water. It is also a good basic food source as it contains the necessary vitamins and minerals that guppies need. However, it is important to choose a high-quality flake food that is high in protein and contains both animal and plant-based ingredients.

Pellet food is also a popular option as it dissolves slowly and doesn't foul the water as much as other types of food. However, pellets can sometimes cause blockages or impactions in guppies, so it is important to pre-soak them before feeding.

Wet food includes frozen and live options, such as mosquito larvae, tubifex worms, and brine shrimp. Guppies enjoy eating live wet food, but it is important to avoid giving them live worms as they may carry harmful bacteria. Frozen wet food is a safer option and provides extra nutrients that are not found in dry food.

In addition to commercial food, guppies can also be fed homemade food such as boiled eggs, beef heart, and vegetables. It is important to ensure that any homemade food is chopped into small pieces that guppies can easily eat.

Overall, it is important to offer guppies a varied diet that includes both animal- and plant-based foods to ensure they get all the necessary nutrients.

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Guppy lifespan

Guppies are a popular choice for home aquariums, but their lifespans can vary depending on a range of factors.

In the wild, guppies tend to live for around two years. Their lifespan is influenced by factors such as location, predators, and environmental conditions. For example, guppies in high-predation environments have been found to suffer higher mortality rates, while those in low-predation environments may live longer due to lower reproductive rates.

In captivity, guppies are expected to live for up to five years. However, estimates vary, with some sources claiming they can live for three to five years, while others suggest they may only survive for six months to a year after being purchased. The lifespan of captive guppies depends on factors such as water quality, diet, stress levels, and tank conditions. Maintaining good water quality, providing a suitable diet, and creating a comfortable environment can help prolong their lifespan.

The temperature of the water also plays a significant role in the lifespan of guppies. In captivity, guppies kept at 74°F (23°C) are expected to outlive those kept at 82°F (28°C). Additionally, the lifespan of guppies can be influenced by their gender and reproductive frequency. Female guppies that get pregnant too often may have shorter lifespans due to the stress of pregnancy.


Guppy health

Guppies are tropical freshwater fish that are popular among aquarium owners due to their vibrant colours, peaceful nature, and ease of breeding. However, they are susceptible to various health issues, and it is important to take proactive measures to ensure their well-being. Here are some key considerations for maintaining the health of guppy fish:

Water Quality:

Poor water quality is one of the most common reasons for guppy mortality. Guppies are sensitive to water conditions, and suboptimal environments can lead to health issues and eventual death. It is crucial to maintain the right water temperature, pH levels, and nutrient composition. Guppies prefer water temperatures between 72-82 °F (22-28 °C) and a pH level of 7.0 or higher. They thrive in hard water with ample calcium, magnesium, and other essential minerals. Regular water testing and adjustments are necessary to create an optimal environment for guppies.


Guppies are prone to begging for food, and overfeeding can lead to constipation and other health issues. It is important to feed adult guppies once or twice a day, providing only as much food as they can consume within one minute. For fry, increase the feeding frequency to three to five times a day but ensure that each meal is smaller to avoid fouling the water. A varied diet, including bloodworms, brine shrimp, flake foods, pellets, and vegetable matter, is recommended.

Tank Setup:

Guppies should be kept in groups of at least three, with a minimum tank size of 5 gallons for three guppies. However, larger tanks of 10 to 20 gallons are preferable, especially if you plan on breeding them. Guppy-only tanks can be visually stunning due to their colourful fins and energetic behaviour. It is important to provide hiding places, such as live plants, for the fry to escape predation by larger fish. Java moss is an excellent choice for cover and can also help maintain water quality as guppies graze on algae.


When selecting guppies for breeding, it is essential to consider not only the desired physical characteristics of the offspring but also the health of the parent fish. Choose the healthiest individuals to minimise the chances of passing on faulty genes or diseases to the next generation. Signs of poor health in guppies include visible fungal infections, fin/tail rot, and bladder inflammation.

Disease Prevention and Treatment:

Guppies are susceptible to various diseases, including bacterial, parasitic, and fungal infections. Maintaining good water quality, providing a balanced diet, and regularly monitoring the fish are crucial steps in disease prevention. Common guppy-specific diseases include ich (white spots), velvet (gold dust on the body), fin rot, and flukes, which can be treated with appropriate medications. However, some diseases, such as guppy fish tuberculosis, currently have no cure, and infected fish should be removed from the tank to prevent the spread of the disease.


The quality of guppies obtained from big pet stores may be inferior due to inbreeding for desirable traits like colour. These guppies often have poor genetics, which can lead to early death. It is recommended to source guppies from reputable breeders, as they tend to have better genetics and can produce healthier and more vibrant offspring.

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Frequently asked questions

Guppies (Poecilia reticulata) are a species of small tropical freshwater fish that are extremely popular for home aquariums. They are native to South America and are known for their bright colours and lively personalities.

Guppies are omnivores and eat a variety of food, including algae, invertebrates, insects, and plant-based food.

Guppies have an average lifespan of 2-3 years in captivity, but in the wild, they usually live for around 2 years.

Guppies can survive in a wide range of temperatures, but the ideal temperature for healthy guppies is between 72-82 °F (22-28 °C).

Feed adult guppies once or twice a day, and only as much as they can eat in one minute.

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