Hot Water Fish

Mosquito fish

  • Scientific name: Gambusia affinis
  • Common Name: Mosquito Fish
  • Aquarium size: 60 liters
  • Temperament: Aggressive
  • Temperature:  Between 18ºC and 27ºC
  • pH: Between 6.0 and 8.0
  • Diet: Omnivore
  • Length: 4 centimeters for the male, 7.5 centimeters for the female


The mosquito fish (Gambusia affinis) , receives its name for being a predatory species of mosquitoes . In some areas of the world, it has been introduced to keep mosquito pests under control with good results, however, because it is a tremendously resistant and voracious species, it has had detrimental effects on the ecosystems where it has been introduced.

It is a very resistant species, which will adapt well to almost any type of warm water aquarium , but with a small problem, they are very competitive, they will constantly be stealing the food of other species and disturbing the smaller fish.

They are not a very suitable species for a community aquarium.


We are facing a fish from the Poecílidae family . Much of its morphological characteristics correspond to those of the group.
They have a cylindrical and elongated body (tapered shape), with the mouth oriented upwards, as corresponds to a surface predator.

Their fins are transparent (they do not have an obvious color), stiff and short. The dorsal fin has between 7 and 9 soft rays, beginning in the middle of the back.

They do not have a striking and strident coloration, like other fish of the same family, they are green to grayish blue, with light brown tones and black spots.

Some differences can be observed between the male and the female of the mosquito fish(sexual dimorphism).

First, there is the size. While the male is about 4 centimeters, the female reaches 7.5 centimeters.

The male has a gonopod, which is the sexual organ of these fish (similar to the penis). It is most evident when the fish is at rest.

Regarding coloration, the female has a ventral black spot , which is also more bulky than in males.

Distribution and habitat

Its origin is in Mexico and the southern United States , although it can currently be found in more than 60 countries around the world, due to its introduction as a species to control the population of mosquitoes, such as those of Malaria or Encephalitis.
It is considered one of the 100 most harmful invasive alien species in the world. In the areas where it is introduced, it causes serious imbalances in the ecosystem, cornering the native species, as in the Dominican Republic, where it has displaced native species of Poecílidos.

In the wild, it prefers shallow waters with great vegetation, that do not have much movement or are totally still, the perfect place for the proliferation of mosquitoes, its favorite food.

Aquarium conditions

The size of the aquarium will depend on the amount of fish that we are going to introduce, as I have said, it is a species that is better kept alone due to its competitiveness.
For a small group of 20 to 25 specimens they would be perfect in a 60 liter aquarium. In a small aquarium of 12 or 15 liters, we could raise a couple without any problem.

As for the decoration and plants of the aquarium, it must be profusely planted, with very resistant plants (Eg. Java fern ) , since they nibble everything.

The water temperature must be kept between 18ºC and 27ºC, with a pH between 6.0 and 8.0.

Filtering should be smooth, as they don’t like currents.


It is an omnivorous fish , which does not present major feeding problems. He will gladly accept dry food , although his favorites are live and frozen prey, of which we must try to make them the stronghold of his diet.

As a complement, we can add vegetable contributions to your diet , such as spinach, peas, lettuce and cooked chard.

Behavior and compatibility

It is not a really aggressive fish, it is rather annoying. Because he is very active and competitive, he will be constantly stealing food from his aquarium kin.

Small fish will be intimidated, and will bite their tails at the slightest opportunity.

It is recommended to keep it alone, for all these reasons, but if we introduce it in the community aquarium, it is best to introduce a small group , in which there is only one male and 3 to 5 females, to reduce its aggressiveness towards other species.

If we keep more than one male in the aquarium, you will observe more than one territorial dispute, even in those aquariums where they are kept as the only species.


The reproduction of the mosquito fish is so simple, that the difficult thing is that they do not reproduce if you keep males and females in the aquarium, since they are fertile within a few weeks of their birth.

No special conditions are recommended as long as the temperature and pH are within acceptable parameters.

If there is a recommendation, as long as we want a high success rate in reproduction, since the adults can eat the fry: maintain a breeding aquarium, which can be placed in an area of ​​the community aquarium.

When the female has spawned, we will extract her from the breeding aquarium and return her to the main one.
The fry can be reared with prawn nauplii and powdered scales, from birth.


Although it is not a very popular fish among aquarists, it is very easy to care for. It adapts perfectly to all kinds of situations, so a newbie has little chance of failing raising the mosquito fish.
Ideal for a small aquarium, which requires little maintenance.

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