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Tetras and alike - Zoopet Aquariumguide

Tetras and alike

Written by Kjell Fohrman

The characins are among the best-known and most popular aquarium fishes. Most aquarists will keep neon and/or cardinal tetras at least once. The best-known characins of all are, however, not especially common in the aquarium, namely the piranhas. This because they grow relatively large and are known for their aggressiveness. The piranhas are, however, not especially aggressive in the aquarium, and are actually rather cowardly. Moreover their rapacity in their natural environment has been somewhat exaggerated.

Characins are found mainly in Africa (approx. 200 known species) and in South America (more than 1000 known species). The natural habitat of most characins is clear, oxygen-rich rivers where the water has a neutral or slightly acid. An aquarium with characins should therefore must have efficient filtration to keep the water clean and create surface movement of the water. The pH should preferably not be above 7 and absolutely not over 7.5. Characins are also very often elongate, fast-swimming fishes which do best in a long aquarium. Most people know that characins are shoaling fishes and that for this reason it is best to keep a good number of each species in the aquarium, at least 10 but preferably even more. The characins also seem to have some kind of signalling system so that they can, for example, warn each other of danger or communicate the presence of food. They are also very sound-sensitive and react very quickly.

The tetras are among the most famous and popular aquarium fish. Most aquarists have or have had cardinal and/or neon tetras at some point. We could list many more small tetras as they are also very popular aquarium fish. 

What is not considered is that this group of fish also includes many species that grow very large. An example of these are the species in the genus Colossoma where some species can grow up to one meter long. The most famous of all tetras is also a species that grows quite large (about 35 cm), namely the piranha (Pygocentrus nattereri). Although it is the most famous, it is not very common in aquariums. The reason for this is that they grow quickly and are known for their aggressiveness. In an aquarium environment, however, the piranhas are not particularly aggressive, they are even quite cowardly. Even their predatory behavior in the natural environment has been greatly exaggerated.

The popularity of tetras as aquarium fish has many reasons, such as the fact that they are very beautiful and easy to care for. Many of them are also relatively easy to grow, which means they are cheap to buy. Another factor is also that there are so many different species and that in this way there is something for every taste.

There are also other interesting aspects of characins such as that they have some kind of signaling system. This means that they e.g. can warn each other of danger or notify if there is food. They are also very sensitive to sound and react very quickly.

Biotope aquarium with tetras.


In the wild, most characins live in clear, oxygen-rich rivers. Therefore, an aquarium with characins must have an effective filter to keep the water clean while creating a surface water movement. Often characins are elongated, fast-swimming fish, which means that it is a clear advantage to have a long aquarium. The bottom material can preferably consist of relatively dark sand. A lot of plants (preferably fine-leaved) also fit well into a tetra aquarium because very few characins are herbivores. Many species also like to have some floating plants in a corner.

A tetra aquarium is easy to set up because they do not dig or burrow in the bottom.

Tutorial how to setup an aquascape with tetras.


In their natural environment, they usually live in water that ranges from neutral to very acidic. In an aquarium, they should never have a pH that is above 7.5 and it is best if it stays just below 7 (there are of course exceptions). As previously mentioned, it is important that the water is clean and rich in oxygen and that you therefore take care of the water changes.


In the wild, the vast majority of characins are predatory fish that feed on small invertebrates and rums. Although they are predatory fish, few of them are fish eaters and in aquariums the majority are very peaceful and like to eat flake food or granules. Freezer food is of course appreciated.

A few species are herbivores such as Distichodus from Africa and Leporinus from South America. The herbivores must be given a vegetable feed and are perhaps not so suitable in an aquarium with fine-leaved plants.


Most people know that tetras are schooling fish and that for this reason you should have quite a few of each variety (at least 10 but preferably even more). Keeping many of the same species together is also significantly prettier than mixing too many species in an aquarium (so-called fish soup).

When keeping these fish together with other fish, it is important to take into account which species you have. Placing neon tetras and piranhas in the same aquarium is not particularly successful.

Most characins mix well with other fish that have similar demands on the water and are not too predatory (most characins are small fish). They fit e.g. good with many moths (Corydoras, Otocinclus etc.), dwarf cichlids (e.g. Apistogramma) and various rasbora species.


The vast majority of characins are rum dispersers and spread their eggs among fine-leaved plants. They do not carry out any brood care and are even space robber. Therefore, they are usually best grown in special breeding aquariums.

A culture aquarium of 25-30 liters is sufficient for the smaller species. The aquarium does not need bottom material, but must contain a thermostatic immersion heater, spawning substrate in the form of fine-leaved plants such as Eichhornia, Myriophyllum or Vesicularia, and a small filter. As a filter, you can use e.g. a fine-pore air-driven foam rubber cartridge. The filter material must be so finely porous that the fry do not get stuck in it.

After that, it's about finding a playful couple. For some time before placing them in the breeding aquarium, you should feed them abundantly with live food such as black mosquito larvae, which seems to stimulate their playfulness. You often see a couple sticking together and seeming playful. The males are usually somewhat slimmer and have a more elongated dorsal fin, while the female is rounder. In the breeding aquarium, feeding should be extremely sparing.

After the pair have played and spread the rum among the plants, they are moved from the breeding aquarium. The number of eggs laid and how long it takes for them to hatch varies between the different species. As a rule, however, a few hundred eggs are laid and they hatch after 2-5 days.

At first they can be fed with infusoria and then with newly hatched artemia.


As a rule, the tetras are hardy fish that are easy to care for and do not suffer from diseases if you give them a suitable environment.

However, some species are a little more sensitive than others, such as e.g. carbends (including the genus Carnegiella) and cardinal tetras (Paracheirodon axelrodi).

Carnegiella are easily affected by the so-called white dot disease and may need to be medicated against this. It is considerably more problematic to cure the cardinal tetras affected by the so-called the neon sickness.

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