Cold Water Fish


  • Scientific name:  Cyprinus Carpio
  • Common Name: Carp Fish, Koi Fish, Koi Carp
  • Aquarium size: 200 liters
  • Temperament: Calm
  • Temperature:  Between 17º and 24ºC
  • pH: Between 6.8 and 8.5
  • Diet: Omnivores
  • Length: Up to 90 cms


The Common Carp Fish, Cyprinus Carpio , is one of the most common fish in the world. Its capacity for adaptation is such that it is possible to find it on all continents, except Antarctica, where temperatures are not good enough.
It is closely related to the Goldfish (Carassius auratus) , with which it could hybridize, under the right conditions. They both belong to the Cyprinidae family
It is not exactly the typical fish for an aquarium, but nevertheless, ponds with carp are very common, where they can develop normally, withstanding almost any type of inclement weather … we are talking aboutcold water fish .


A fully developed tent can measure between 60 and 90 centimeters in length and achieve a weight that could reach up to 8 or 9 kilos.
That is why it is not a «typical» fish for an aquarium, even if it is cold water, they are fish designed to breed in ponds, where they will develop to perfection.
They are elongated fish, with different colors depending on the variety and even the quality of the water . The back and the fins are usually dark, with coppery or golden flashes, the ventral area has greenish yellow tones, although these colorations change completely when we talk about the Koi Carp fish, which is still a common Carp.
It has a protractile mouth, in which two pairs of barbels are arranged. The upper pair goes quite unnoticed due to its size, while the lower pair is long and quite obvious.
Its robust body is covered with long and thin scales, although this circumstance can also change depending on the variety, since the mirror carp has very large and scattered scales, while the Korean carp does not have scales.
Carp males can be differentiated from females, due to the fact that there is a certain sexual dimorphism. In males, the ventral fin is longer than in females.

Koi Fish or Koi Carp

The Koi Fish or Koi Carp, is an ornamental variety of the Common Carp … come on, they are exactly the same carp, with the same morphological characteristics, except for their attractive colorations, the result of the selective breeding of carp. It is the variety of carp that we can see in most ponds.
Originally, Koi Fish was a fish that Japanese farmers raised in ponds to have fish supplies.
It is only from the XIX century when, almost accidentally, the selective breeding of carp begins to reach the Koi Fish.
Farmers found that some varieties had a brighter coloration, which made them easy prey for predators.
It was striking to them and they began tobreed and cross these specimens, to get what we know today as Koi Fish.
Their greatest popularity comes from the beginning of the 20th century, after the annual Tokyo exhibition of 1914. The selective breeding of ornamental carp in what are known as Koi ponds, gained great popularity, jumping the borders of Asia to the rest of the world .

Distribution and habitat

The common carp fish is native to Europe and Asia , although it is in China and Japan where carp breeding became a social phenomenon, with the figure of the professional carp breeder coming into existence.
Its natural habitat is areas of slow or stagnant waters, rivers and lakes.
The one fish that adapts perfectly to almost any type of condition. We can find them in all kinds of waters, some highly polluted, because they can withstand low levels of oxygen.
Their preference is temperate waters, although we use them as a cold water fish, because they are ectothermic fish, they have the ability to adapt to environmental temperature, regulating their body temperature.
Due to this brutal adaptability to all types of environment, they are present on all continents except Antarctica.
It is currently considered a harmful invasive species, because it is able to corner and eliminate other native fish species.

Aquarium conditions

A carp aquarium is possibly not the most original in the world, however and by choosing the varieties well, we can have a really interesting aquarium.
The great advantage of having a common carp aquarium is that it is quite easy to maintain for any beginner. I have already commented that they are fish with a great capacity for adaptation, with a life expectancy that can reach 60 years of age !!
The optimum temperature conditions for an aquarium or pond for common carp fish is between 17ºC and 24ºC, with a pH between 6.8 and 8.5.
The bottom of the aquarium should be gravel,and in the decoration you can add all kinds of plants, provided you know that they are fish that like to move the substrate and can lift them, so you can also choose to use plastic plants.
If we raise carp in a pond, the number of plants can increase, even using water lilies and other types of floating plants.
In any case, we must know that it is very important to manage the amount of nitrites in the water well, because although they support the lack of oxygen well , depending on whether our variety of carp is more decorative, it can be less tolerant.
In any case, it is better to maintain good water quality, for the health of our tents and to better enjoy their presence.

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Carp are omnivorous fish. In freedom they will eat all kinds of aquatic plants, insects and crustaceans, with a special predilection for plant substrates.
In the aquarium it is convenient for us to maintain their health, for which we will provide them with a balanced diet, consisting of quality dry food, mixed with live or frozen vegetables and insects, as well as some crustaceans.
Vegetables can be of all kinds, we can offer them lettuce or spinach leaves, they will eat it all.

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Behavior and compatibility

They are docile fish that need the presence of other individuals to feel good, so it is recommended to have a small group of 6 to 7 individuals.
The space to share is the only thing that can really cause problems, because in a small or overcrowded space, there can be cases of aggressiveness.
As they are cold-water fish, with great growth (they can gain up to 1 kg per year), it is very difficult to share space with other species.
They could share it with other Cyprinids, like some varieties of Goldfish, but we run the risk of hybridization.


The age of sexual maturity, from which we can think of carp breeding, is 4 years, although males can reach sexual maturity much earlier.
Carp breeding season begins in spring and ends in early summer.
It is possible to modify this situation in the aquarium, but not in a pond, where the temperature conditions are difficult to modify.
In the aquarium, we can lower the temperature previously, to simulate the winter temperatures where the fish are somewhat lethargic, to gradually raise the water temperature and promote the mating of spring.
Females usually lay about 300,000 eggs, which are fixed to the bottom of the aquarium, where the male will fertilize them.
Once fertilized, the eggs will take about three days to hatch, as long as the temperature is around 30ºC, if the temperature is lower, this period of time is extended.


If we are going to breed Carp fish in the aquarium, it would be advisable to use the Koi carp variety.
Koi carp is a variety of common carp, but smaller in size, and with a much more showy coloration.
Its origin is in Japan, where they have been raising carp for ponds and aquariums, for hundreds of years.

Carp fish photos

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