Guppy Fact Sheet

Guppy Fact Sheet The Guppy, Poecilia reticulata is an attractive and normally peaceful fish. It was named after Robert John Lechmere Guppy who discovered this fish in Trinidad. He believed that this was a previously undiscovered fish. After being scientifically described, the fish was called Girardinus guppii. The common name of Guppy was given the fish.

The Guppy males tend to have a smaller body and bigger fins than the female. The fin underneath the fish in about the centre of the fish’s body (the anal fin) is long in the male and is used in fertilisation. The male is capable of pointing it forwards so it can make contact with the female and transfer the sperm. In the female, this fin is triangular in shape. The males tend to be much more colourful than the females. Modern female guppies often have good colours, but the wild ones did not. Modern Guppy males tend to have purer colours, while the wild ones tend to have more varied ones. Often the wild males have more colours on each fish.

It was later found that the fish had been previously discovered by Wilhelm C. H. Peters, described and named. The fish is now usually called Poecilia reticulata. The most common of the common names is ‘Guppy’. There are several other common names including ‘Rainbow Fish’ and ‘Millions Fish’. The name Rainbow Fish is appropriate to its many and varied colours, but is misleading because of the several other fish with the same name. I prefer the name “Guppy’. However, I would note the name ‘Guppy’ is sometimes used for other fish. Fish I have seen called ‘Guppies’ include goldfish, Neon Tetras, Zebra Danios and Gambusia. This is simply misleading and can be confusing.


Guppies are native to several Caribbean islands and north western South America including Barbados, Guyana, Netherlands Antilles, Trinidad and Tobago, the US Virgin Islands, Venezuela and Brazil.


The Guppy is a popular aquarium fish. It can be kept with other small peaceful fish, including Platies, Swordtails and Mollies. It is in the same family as these fish and is in the same genus as Mollies. Other fish suitable as companions are White Cloud Mountain Minnows, Neon Tetras, Cardinal Tetras, Siamese Fighting Fish, Peppered Catfish and other Corydoras catfish, Cherry Barbs, and other small peaceful fish.

Note that many of the fish just named are schooling fish. I would recommend that these be kept in groups of at least four, and preferably more. The Guppy is not a very strongly schooling species and can be kept singly or in small groups, although I certainly prefer larger numbers. It is both the way they usually occur naturally, and they look good. A tank of the highly coloured Guppies is a beautiful sight. Males and female guppies can be kept together although if they are I suggest that at least one female be kept for each male. If you keep several males with one female, all the males want to mate with the female and do not give her much peace.

Fish I would not recommend as companions for guppies include Black Widow Tetras, Serpae Tetras, Buenos Aires Tetras, Paraguay Tetras, Red Eye Tetras, Tiger Barbs, Rosy Barbs, Paradise Fish, Galaxias, and any other fish that can be fin nippers. Larger fish are also generally not suitable companions for Guppies.


The Guppy is easy to feed. They are omnivores like most fish,and benefit from some vegetable food including algae. Guppies will eat most fish food. I suggest a good flake food as a basis for the diet, if possible supplemented with other food to give variety. Good flakes include the Wardley Total Tropical or Total Colour. As well as Wardley there are many other reputable manufacturers of fish food who make excellent foods. Other foods can include live food like Daphnia. Mosquito larvae (Wrigglers) are an excellent food. In the wild, Guppies will eat a lot of these. Their upturned mouth is well adapted to eating wrigglers. Blood Worms are related to wrigglers and are also a good food. Frozen Blood Worms are also good, as are several other frozen foods. Live or frozen Brine Shrimp are good. I also find that Guppies will benefit from dry fry food as achange.

Do not over feed your fish. I suggest feeding once a day, but not too much. For most types of food the fish should have finished it in a couple of minutes. Guppies are good eaters and generally will get the food quickly. Larger food including Algae Wafers is also good. Because these are hard, the Guppy will take longer to eat them.


Guppies generally thrive in fairly hard, slightly alkaline, water. They can tolerate very large amounts of salt in the water. In some countries they are bred in water which is a mixture of half fresh water and half sea water. The Guppies thrive in this water, but these fish can cause problems when people put them into normal fresh water aquariums. As well as having to be acclimatised to the fresh water, the Guppies have not been exposed to columnaris disease. These fish can die very quickly in a normal aquarium unless strong treatment is done quickly. To get immunity the fish have to be exposed to the disease, and the disease cured.

Rain water is not good water for guppies although many people have used it successfully. If this is the water you have, I suggest using a rainwater conditioner (A mixture of salts). If you are using tap water (as I do), make sure you get rid of the Chlorine or Chloramine.

For a tank of mixed small tropicals, I suggest a pH of 7 and a moderate amount of salt and hardness. In most places normal tap water, with the Chlorine or Chloramine removed and the pH adjusted to 7 is suitable for Guppies, and to a mixed community. If in doubt about your tap water, I suggest visiting your local aquarium store. They should know about the local water.


The Guppy is a tropical fish. However, different strains of Guppy have different tolerances to low temperatures. I have even heard of strains that are claimed to be able to tolerate temperature down to 4Ì? C (39Ì? F). I have never encountered any of these. Once I heard of a creek to the north of Adelaide that was supposed to have a naturalised strain of Guppies. I searched for the creek. I was able to identify the creek from the description I was given. There were no Guppies in it. (Actually, there was not even any water.) Although I tried to find where the Guppies would have gone, I was unable to find any Guppies. I suspect that this was a case of mistaken identity of the fish.

As a general thing I would not suggest a temperature of lower than 18 degrees C (65 degrees F). Guppies will certainly tolerate up to at least 32 degrees C (90 degrees F), and probably higher. Although I sometimes give the maximum and minimum temperatures types of fish can tolerate, it needs to be remembered that subjecting fish to their limits is not good and you are stressing the fish very badly. Stress will leave the fish very vulnerable todisease.

I generally set the thermostat at 24 degrees C (75 degrees F) although some people prefer a few degrees higher, especially for breeding.


The modern Guppies have been selective bred for colour and fin length, as well as other external characteristics. In the process they have lost much of the original hardiness of the Guppy. The life span of the Guppy now is often no more than a year.

Pest Fish

The Guppy has been introduced to every continent except Antarctica. In some places it is causing considerable damage to the native fish of the areas it has been introduced to. You should not release aquarium or pond fish into the wild, and you should ensure that they cannot get introduced accidentally.

It is worthy of note that many of the most destructive introduced fish and other animals have been introduced deliberately, often by government agencies.