Piranhas | All about Foods, Size, Place, diseases

Everyone comes to mind when they call us a piranha to Steven Spielberg’s movie in which these fish devoured men. Therefore, it may be surprising that most popular beliefs about these species have been incomplete simplistic or simply inaccurate. In this article you will find all the information related to piranhas so that you can draw the conclusions yourself.

What is the origin of the word piranha?

The word piranha, of Tupi Guaraní origin, has been used since ancient times in a large part of the Amazon basin.  In the Tupi language, pyre means fish, and Ranha or sanha refers to the teeth . Therefore, the piranha is known as the fish with teeth.

What do aquarium piranhas eat?

In nature, piranhas have a varied diet . And, in captivity they should seek a similar diet. Only a wide variety of nutritious foods can avoid dietary deficiencies and health problems.

The amount of food needed to keep piranhas in good health depends on their age. If they are fed more than necessary, these fish become overweight very quickly , a very frequent fact that should be avoided.

Live foods

Fortunately there is a minority of aquarium fans that seems to enjoy watching piranhas and other predatory species attack and devour other fish. Although piranhas are reluctant to accept food in the form of flakes or granules, the use of live fish as food is decidedly not necessary for them to be in good health.

In addition, this practice represents a great risk to the welfare of the fish. Goldfish are carriers of a large number of internal and external parasites and diseases that can be easily transmitted to piranhas.

Ich, trematodes, anchor worms and hexamite are some of the potentially serious problems that can be transmitted to the interior of the aquarium through fish that are used as prey.

At first, newly acquired piranhas may be reluctant to accept non-living foods, which shows their shyness, rather than their eating habits.

If you still believe that you should feed your piranha fish alive, you should first submit them to a quarantine period with a treatment against trematodes . This entails the inconvenience of having to permanently dedicate a quarantined tank to the fish that will serve as prey.

There are less dangerous live foods for the health of piranhas, such as earthworms and live artemia , which will help your piranhas feed without any inconvenience.

Frozen food

The basis of the piranha diet should be formed by a good assortment of frozen foods . Freezing destroys most parasites. Here are some of the suggestions:

Whole fish Frozen fish used as bait are one of the most recommended foods. They provide the nutritional benefits of whole fish. In addition, they provide the necessary protein as they are also an excellent source of vitamins and minerals. They can be found in most stores of animals and fishing equipment.

Frozen Krill : These small marine shrimp not only provide the necessary proteins and trace elements, but also their shells are an important source of carotenes, which contribute to the development of the colorful red and yellow hues of our piranhas.

Other recommended foods

Commercial preparations : in pet shops can be found many brands of very complete frozen food for aquarium fish, which are prepared in a gelatinous base. These foods incorporate ingredients of animal and vegetable origin very balanced for our fish.

Processed dry foods

This category includes a multitude of food for piranhas in the form of flakes, granules and bars . In them we also include freeze-dried foods. Although in general they are balanced foods, piranhas do not usually accept it too well, but with patience our animal will get used to it and eat it without any problem.

What size does the aquarium have to be?

Our piranha aquarium must be large enough to house the fish when it reaches adulthood.  A 75 L tank may be suitable for half a dozen 5 cm piranhas, but the minimum size needed for two or three adult red-bellied piranhas will be approximately 200 liters . If you are not willing to keep an aquarium at least this size, you should rethink having piranhas at home.

Where should I place the aquarium?

There are many factors that must be taken into account when deciding the location of an aquarium for piranhas, Among them are:

  • The weight of the aquarium : a liter of water weighs a kilogram. The glass aquarium of about 200 liters, fully assembled, with a substrate of gravel, rocks, other elements and full of water weighs at least 270 kg. This makes it essential that the aquarium stand is sturdy or your aquarium glass will break.
  • Natural light:  for aesthetic reasons such as maintenance, it is best not to place the aquarium in front of a window. The intense direct light will favor the excessive development of algae, so that the rented water a greenish tone unattractive and in summer the aquarium could get too hot.

What maintenance should I give to the aquarium?

Routine maintenance and careful observation of the aquarium, although they do not take much time, are essential to have a good aquarium always healthy and beautiful and disease free for our fish.

What temperature does the water in the tank have to have?

The optimum temperature at which must be our aquarium will be between 22 ° and 28 ° C .

 Can you hear?

Piranhas have a good ear . They have an organ called a labyrinth located in the skull, which contains the inner ear and an organ that controls balance . Weber’s device transmits these sound waves to the ear.

Can you see the piranhas?

The fish’s eyes have a flat and rigid crystalline cornea. Piranha eyes are better suited to see during the day, but your retina may also be provided with a reflective layer that intensifies your night vision . Like the other fish, they have no eyelids.  

Are they aggressive?

Anyone who has piranhas in their home should use precautions when handling and during the maintenance of the aquarium. The sharp teeth and powerful jaws of large piranhas can cause serious injuries and even cleanly amputate a finger. Therefore, aquariums and those with small children are advised to avoid having piranhas as pets. If you receive a bite from one of them, you should see a doctor as soon as possible.

Here you have a video with what these piranhas are capable of doing. Better not tempt fate

When buying a piranha, how can I know if it is healthy?

Newly imported piranhas seen in store tanks are often missing fin portions, due to the aggressive behavior of other members of the same species . Both those who capture piranhas and those who export and import them, usually keep them in overcrowded conditions, which increases their fear and aggressiveness. If one thinks that the young piranhas of most species and, also the adults of many others, feed primarily on fins, it is not surprising that many of the specimens that are for sale have mutilated fins.

When the time comes to select the piranhas you want to buy, follow the same criteria as with any other aquarium fish. Healthy piranhas are active, alert, and eat as soon as they see food. Reject any copy that is emaciated or shows inactivity. Excessive accumulation of mucosa in the body’s fins may indicate an infection by external protozoa . Make sure they do not breathe hard, which could indicate a problem with gills, water in poor condition or a systematic illness.

How should I transport the one from the store to my aquarium?

Piranhas of all species are known for their ability to bite the plastic bags of fish transport. Even those that are double or triple in thickness. The chances of this happening decrease if we first give the fish slightly with a tranquilizer known as ms-222.

I recommend that if it is short distances, be a plastic boat to transport the fish. For longer journeys, each time it must be placed in a different plastic container in which holes have previously been drilled.

When should I put them in the tank?

It is important to acclimatize new fish to the aquarium water conditions, since they probably will not be equal to the store’s waters. Float the bag with the fish in the aquarium until it acquires the same temperature. Then you can drop it in your aquarium.

How can I prevent them from having diseases?

One of the great challenges for the tropical fish fan is the rapid and accurate diagnosis of the diseases that affect the fish. Piranhas are a fairly resistant species with great adaptability, but even the strongest fish can suffer from various diseases. A quarantine period followed by proper maintenance and care will help ensure a better and longer life for the fish .

Poor water quality reduces the resistance of fish increases their sensitivity to disease. It can also cause symptoms similar to those of an infectious disease. We should always check the pH, ammonia and nitrite levels of the water, as well as the temperature before administering a medication Sometimes all that is needed is a partial water change.

An important factor for the treatment of sick fish is the hospital aquarium. It is especially useful to care for injured fish or four a non-contagious disease affects one or two specimens. If it is a very contagious disease that affects most aquarium fish, it is best to administer the treatment in the original tank.

How do I owe the wounds I suffer?

A minor wound in a healthy piranha , especially if it only affects the fins, usually heals easily without the need for treatment . Clean and well filtered water with few dissolved organic elements favors a quick cure and helps prevent the occurrence of fungal or bacterial infections.

If the wound is important, the situation is different. If the aquarium is home to a group of piranhas, it is advisable to transfer our fish that present a major wound to a hospital aquarium as soon as possible . Piranhas can frequently display cannibalistic behavior with tank mates who are in poor condition.

Piranha that looks like serious wounds should be given a prophylactic treatment based on broad-spectrum antibiotics to prevent infections. One of the best is nitrofural, which should be used following the manufacturer’s instructions. Especially effective are products that contain a combination of nitrofurazone and furazolidone . These products are not toxic to piranhas and do not affect biological filtration.

What kind of infections are there?

Bacterial infections

The most common cause of bacterial infections in piranhas are wounds. Bacterial infections, either of the body or of the fins, can be recognized by their blood-like reddish appearance and the rapid deterioration of the tissue. If left untreated, bacteria can reach blood flow and cause a fatal outcome.

Loss of fins

fin rot begins to manifest as darkening or redness at the edges of the fins. If it is not treated, time progresses rapidly to fraying and destroying the fins and then it can be extended to the rest of the body.


Tuberculosis of fish is a much more common disease in these animals than is believed. This is due to the fact that the lesions produced mainly affect the internal organs and are not perceived until an autopsy is performed, which includes performing specialized tissue analysis and microscopic observation. In the natural habitat these symptoms of the disease are chronic and affect all species of fish. It manifests itself because the fish is losing weight, they are indifferent and often separate from the rest of the group.

Fungal diseases

There is a wide variety of internal and external fungal diseases that affect fish but the two most common are those known as body fungi and gill fungi.

External parasites

External parasites can be of different types worms, crustaceans and protozoa. Some are so large that they are easily seen and identified, while others are microscopic in size. If you do not have the possibility to use a microscope, the diagnosis should be made according to the symptoms.

The various kinds of parasites that can affect our piranhas are trematodes, crustaceans parasites, protozoa and external parasites.

Can you have piranhas of different species in our aquarium?

The idea of ​​having an aquarium with mixed groups of piranhas is tempting. So far, not much has been experienced in this regard, but most likely it has little chance of success . With the exception of the Pygocentrus genus, most adult piranhas feed primarily on the fins of other fish, including those of other piranhas. It is shown that the most solidarity species can attack their peers. Even when you have a group of several specimens of the genus Serra Lamus, who normally live in schools, finning can be a problem. We can minimize this problem by putting them in a very large aquarium with a lid, in which each individual can defend their own territory or escape the aggressions of the rest of piranhas.

If you want to have piranhas in a group, I recommend that you make the species of red belly or red piranha.

What aquarium mates can they have?

The mixture of piranhas with other fish in domestic aquariums is a very controversial topic interesting. Possibly the best piranha exhibit I have ever seen is at the Dallas Aquarium point a group of more than 30 adult red-bellied piranhas share a pond of approximately 11,000 liters.

Can you breed in an aquarium?

It should be noted that the breeding of piranhas requires great dedication in terms of time, money and space. A group of 6 to 8 breeding piranhas will need an aquarium of at least 400 to 1000 liters . To avoid fierce struggles and cannibalism, the most supportive species that feed on fins and scales will need more space per piranha than those that naturally live in small groups.

Where can I find breeding piranhas?

Do not expect to find a species of breeding piranha in your usual pet shop. Rarely, adult breeding piranhas are imported from South America. Due to their large size and the need to transport them in individual bags, the cost of transportation is prohibitive. There is also the possibility that they bite the bags and arrive dead. Therefore, only small piranhas are for sale.

I recommend that the piranha breeder acquires a group of young fish and wait until they mature , for which you should wait approximately 2 years, even receiving the best care. By way of advice I recommend that you buy some more piranha since there are always casualties .

Even having a group of mature piranhas, to get them to reproduce you need a lot of skill and luck. Piranhas like to build their nests among the thickets of aquatic plants, so we recommend using them. The best plants when breeding are Vallisneria, Sagitattaria and Bacopa.

What do I have to do to raise them?

I would recommend reducing the amount and frequency of meals and increasing the water temperature to 30 degrees. You can also reduce the frequency and volume of water changes , always trying not to endanger the health of the fish. After a couple of months, filtering and aeration should be maintained and increased and begin to make partial and very frequent water changes. The temperature of the heater can be reduced to about 25 degrees to increase the quantity and variety of food . Hopefully, this simulation of the beginning of the rainy season, which is when they breed in their natural habitat, encourages piranhas to think about starting a family.

Water hardness and pH do not seem to be essential factors , until extreme situations are reached. Piranhas have been raised in soft to moderately hard waters, with slightly acidic and quite alkaline pH values.

What size do they reach?

Piranhas that have been raised in good condition grow rapidly. Black piranha fry reach lengths of almost 2 cm in 6 weeks , and red-bellied piranhas reach 12.5 cm in 8 months . These measures coincide with those achieved in nature, according to existing references. These two species of fish reach maturity at approximately 2 years.

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