A South American freshwater fish found in most rivers in the Amazon and Orinoco basins of the Amazon lowland. Pacu also made their way to Papua New Guinea, where they were artificially bred to help the local fishing industry. The pacu shares common roots with the piranha, being in the genus Serrasalminae, although they have different habits and preferences. Piranha is a carnivorous species, while Pacu is omnivorous, with a vegetative preference. The difference is obvious in the structure of their teeth. The piranha has razor-sharp teeth, while the pacu's are squarer, straighter, and eerily similar to human teeth.
Pacu use its teeth mainly to crush nuts and fruits, but they also sometimes eat other fish and invertebrates. They commonly eat floating fruits and nuts that fall from trees into the Amazon, and in several cases have even attacked the testicles of male swimmers, confusing them with nuts. They earned a dangerous reputation after they castrated several local fishermen in Papua New Guinea. So when the fish were discovered in several lakes in Denmark, and later in Washington, New Jersey and Illinois, there was a bit of panic.
While pacu are not aggressive carnivores like piranhas, their crushing jaw system can be dangerous. One baby needed surgery after a pacu bit his finger at Edinburgh Zoo in Scotland. The manager then commented on the incident by saying that "Paku will eat anything, even a child's wiggling fingers."
These fish are legal in the United States and can be purchased at pet stores. The problem is that many aquarium owners do not realize that pacu can grow over a meter long, which is too long for a typical home aquarium. When a pet outgrows their fish tank, owners end up releasing it into nearby lakes. This explains the fact that the fish began to be found in many bodies of water outside of its natural habitat.
Originates from South America from the vast Amazon River basin. The distribution area covers the territories of Colombia, Venezuela, Peru, Bolivia and Brazil. This species was introduced to Asia, where it successfully took root as a commercial fish.
The natural habitat is river channels and floodplains among tropical forest, regularly flooded during the rainy season. Prefers shallow areas of slow-moving rivers with floating or low-hanging vegetation. Young individuals spend the first months of their lives in floodplains, where there is an abundance of food and a minimum of predators.
Brief information:
- Aquarium volume - from 1000 liters.
- Temperature - 23–28°C
- pH value - 4.8–7.5
- Water hardness - soft (1–15 dGH)
- Substrate type - sandy, soft
- Lighting - dim or moderate
- Brackish water - no
- Water movement - weak to moderate
- The size of the fish is up to 60 cm.
- Food - any, mostly plant-based
- Temperament - peaceful
- Content alone or in a group
Description
The largest recorded length of an adult fish was 88 cm. But usually fish do not exceed 60 cm. Sexual dimorphism is weak, distinguishing a male from a female is problematic.
This species is often sold under the name Vegetarian Piranha, due to its resemblance to this formidable Amazon predator. The red-bellied pacu really does look like a piranha. It has a laterally flattened body and relatively small fins. The color is dark gray. Young fish have a red belly. As they grow older, the red shades are lost.
Nutrition
It feeds on almost everything that can fit into the mouth of this fish: fruits, nuts, fruits, seeds, insects and their larvae, crustaceans, worms, small fish. However, the basis of the diet is still plant-based. In a home aquarium, for example, you can serve pieces of bananas, apples, peaches, carrots, zucchini, peas, and grapes.
Maintenance and care, arrangement of the aquarium
The size of the fish implies a large aquarium with a volume of thousands of liters. When keeping the Red-bellied Paku, equipment is much more important than design. Fish can live in a completely empty tank with a couple of large stones as decoration. Plants are not needed because they will be eaten.
Maintaining a stable biological system in aquariums with large fish requires serious expenses, knowledge and experience, so the selection of equipment, installation of the aquarium and its subsequent maintenance should be handled by professionals. Thus, the details of the content of this species are beyond the scope of this article.
Behavior compatibility
Peaceful, calm and even shy fish. Compatible with many species, except very small ones. Adult large individuals are able to get along with aggressive and predatory fish. Can live either alone or in a group.
Breeding/reproduction
No successful cases of breeding in aquariums have been recorded. The production of offspring is carried out on large fish farms in South America and the Far East using hormones.
Fish diseases
Hardy and unpretentious fish. Health problems arise only when kept in unfavorable conditions and poor quality nutrition. Read more about symptoms and treatment methods in the section "
How would you feel about catching a fish like this?
And this is not some kind of deviation at all, but a completely understandable phenomenon. And you all know this fish...
Pacu is the common name for several species of omnivorous South American freshwater piranhas. The pacu and the common piranha (Pygocentrus) have the same number of teeth, although differences in their alignment are noted; The piranha has pointed, razor-shaped teeth with a pronounced mesial bite (the lower jaw protrudes forward), while the pacu has square, straight teeth with a slight mesial or even distal bite (the upper front teeth are pushed forward in relation to the lower ones). As adults, wild pacu weigh more than 30 kg and are much larger than piranhas.
The designation Pacu is of Brazilian-Indian origin. As soon as large representatives of the genus Colossoma appeared in the aquarium hobby, they immediately received the name pacu. In the Amazon, this word collectively refers to small and medium-sized representatives of the genera Metynnis, Mylossoma and Myleus. At the same time, the species Colossoma macropomum is known as “tambaqui”, and Piaractus brachypomus is known as “pirapitinga”. 
Pacu, along with piranhas, are close relatives of popular aquarium characins such as neons and tetras. The current classification of these fish is complex and, in many cases, controversial. This is because ichthyologists rely on characteristics that may overlap randomly (cladistics) when reconstructing relationships between taxa. In some cases, DNA analysis is carried out, which confuses rather than adds harmony to the arrangement of species. Ultimately, an artificial arbitrary classification results. 
Head profile and teeth of a common piranha (left), head profile and teeth of a pacu (Piaractus mesopotamicus, right)
Piranhas and pacu are members of the subfamily Serrasalminae ("Serrated salmonids"), all members of which have a serrated keel running along the abdomen. However, diet and dental structure are very different between these groups. 
Currently, the pacu includes the following genera: Acnodon, Colossoma, Metynnis, Mylesinus (Mylopus), Mylossoma, Ossubtus, Piaractus, Tometes and Utiaritichthys. Each of these groups includes one or more species. For example, the commercial black and red-bellied pacu are the species Colossoma macropomum and Colossoma brachypomum, respectively, and Piaractus mesopotamicus is known as the Parana River pacu. 
All representatives of pacu inhabit the rivers and streams of the Amazon and Orinoco basins of the Amazon lowland, where they are part of the Neotropical fish fauna.
The fish are often marketed as “herbivorous piranhas.” With the right level of care, they can become responsive pets. However, there is information that calls into question the possibility of keeping fish by ordinary aquarists. Despite the fact that pacu are not as carnivorous as piranhas, and their jaws are designed to crush nuts and seeds, they can pose a danger to humans.
Pacu originally roamed the waters of the Amazon and are now found in North America and Asia after sport fishing was allowed. In 1994, two fishermen from New Guinea died after being attacked by a mysterious creature in a lake that practically riddled their bodies. The men died from loss of blood. As it turned out later, responsibility for this “crime” lay with the pack. These attacks prompted world-famous extreme fisherman Jeremy Wade to travel to this Guinean lake and catch the culprit - a giant killer pacu. Attacks on people and animals are made only by young, immature individuals of the brown pacu. 
Pacu was introduced as a commercial species into the Sipik River in 1994 and into the Ramu River in 1997. Local residents do not like these fish because they eat native species, including young crocodiles, and occasionally attack people.
While pacu are predominantly vegetarian in nature, in Papua New Guinea there are reports of the fish reaching very large sizes and attacking humans. In fact, the largest specimens are caught in this state compared to the rest of South America. They gained notoriety as "egg eaters" after red-bellied pacu in two separate incidents bit off swimmers' genitals and left them to bleed to death in 2001.
Pacu are one of the main commercial species of the Amazon. In addition, due to their resistance to low oxygen levels and low dietary requirements, they are a favorite subject for aquaculture.
Research has shown that farmed pacu taste similar to hybrids of striped bass, tilapia and rainbow trout, but are superior to catfish. In South America, its meat is famous for its softness and sweet taste. 
The brown pacu fish (Colossoma macropomum) reaches a length of 108 centimeters and weighs approximately 25 kilograms, although there are specimens weighing up to 40 kg. Pacu lives in the Amazon and Orinoco river basins and is a freshwater piranha. The appearance of the pacu is reminiscent of piranhas: the body is high, laterally compressed, the eyes are large. Body color ranges from gray to black, with variations. About 10% of body weight is fat.
Brown pacu are usually solitary; juveniles consume zooplankton, insects, and snails. Adult fish are mainly herbivorous, feeding on fruits and other plant foods. Young individuals stay in the river waters until puberty. 
There are predatory fish in European rivers that attack people. However, the worst thing is that the goal of the river predator is male genitals. It is almost impossible to avoid an attack when encountering such a fish, so the authorities in Denmark and Sweden, where several fishermen have already died, are calling on citizens to refrain from swimming for a while.
Scandinavia has already confirmed that several fishermen died from blood loss after being attacked by a predator fish. How this fish got into its unusual habitat is still unknown. This type of fish is called pacu, and it was discovered in the Øresund River in Denmark. In appearance, this fish is as unpleasant as it is dangerous; it has a rather frightening appearance and large teeth. 
These curious-eyed fish usually swim leisurely around the aquarium. Looking at them, it is difficult to guess that these are close relatives of the terrible ones. Yes, the pacu fish is from the piranha family, but it mainly feeds on plant foods and does not pose a danger to humans.
The name pacu is used for several large species of fish of the piranha family (Serrasalmidae) that live in the rivers of South America. The number of teeth in the common piranha (Pygocentrus nattereri) and the pacu is the same, but their structure is very different. The teeth of the predatory Pygocentrus nattereri (also called the red piranha) are pointed with a clearly visible mesial bite (with a protruding lower jaw).
Pacu teeth are straight, rectangular (sometimes called square). The bite may be slightly mesial or distal: the teeth of the upper jaw are slightly protruded, and the upper jaw may protrude slightly forward. Or both jaws are in the same position: neither of them protrudes.
Which pacu are popular among aquarists?
The homeland of all pacu is the reservoirs of the Orinoco and Amazon basins. They are part of the neotropical fauna. They are often sold as herbivorous piranhas. But in order for pacu to become real pets that delight the owner, it is necessary to provide proper conditions and care for them. After all, these fish are not small! Typically, aquariums contain black (aka brown) and red pacu.
About the Latin names of pacu
The Latin scientific names used in this article correspond to the latest updated fish database data. Based on the data from this site, it is concluded that the Russian names black and brown pacu refer to the same species, the scientific name of which is Colossoma macropomum. Acceptable (correct) synonyms are the following Latin names: Colossoma nigripinne and Piaractus macropomus. The authors of articles on some Internet resources consider the black pacu as a separate species and use the name Colossoma brachypomum for it, which is erroneous, because according to the fishbase website this name is synonymous with the Latin name for the red pacu (Piaractus brachypomus) and, therefore, applies to Russian name for red paku.
About the red pacu
Several Russian names are used for this pack. Most often it is called the red pacu, sometimes the name red-breasted pacu is used, and very rarely - the two-toothed colossoma. According to fishbase, the currently accepted correct Latin scientific name is Piaractus brachypomus, which has synonyms: Colossoma bidens means two-toothed colossoma; the second frequently used synonym is Colossoma brachypomum. The name Colossoma branchypomus cannot be used for this species because there is a typo in the last syllable.
How to distinguish a red pacu from a red piranha
Due to its appearance, the red pacu fish at a young age is often mistaken for the dangerous predatory red piranha Pygocentrus nattereri. Especially if she swims in a species aquarium, near which there are no labels with the names of the fish. Indeed, these two fish are very similar and have almost the same characteristics:
- laterally compressed tall body with small silvery scales;
- the gill cover in the lower part and the belly are red;
- fins (paired ventral and anal) are also bright red;
- the edge of the caudal fin with a striking black stripe.
The main difference between these two types is the structure of the teeth. Let's look at the photo of the red pacu fish, pay attention to the open mouth. We see rectangular teeth, very reminiscent of human ones. The teeth are large and strong with a wide top, so the fish can easily crack nuts.
But is it really necessary to look into the fish’s mouth to understand whether a red piranha or a pacu is swimming in an aquarium? And how to do this? No need to look into your mouth. Take a close look at the closed jaws of the fish. If the lower jaw protrudes forward very strongly, there is a bloodthirsty piranha in front of you. If the jaws are approximately the same, it is a vegetarian red pacu. 
Habitat, age and size
The habitat of the red pacu or two-toothed colossoma are numerous tributaries of the Amazon and Orinoco and the rivers themselves. There is evidence that this species has been recorded in Argentina.
This is an omnivorous fish, but the basis of its diet in natural conditions is nuts, which it cracks with its flat teeth and strong jaws. It practically does not eat meat; it can feed on insects and rotting plant remains. This is a fast-growing species and can reach 30 centimeters in length by the end of the first year of life. It is the subject of aquaculture and commercial fish farming. A popular species among aquarists.
The maximum recorded length of a red pacu is 88 cm, the largest weight is 25 kg. There is information about the maximum recorded age of this species, which was 28 years.
About the brown pacu
The brown pacu is best known by its Latin name Colossoma macropomum, although there are also synonyms: Colossoma nigripinne and Piaractus macropomus. In nature, they live in the Orinoco and Amazon basins.
Position in the fish system: class Ray-finned fish, order Cyprinidae, suborder Characinidae, family Piranhaidae.
An external difference, characteristic of all fish of the characinoid suborder, is a small adipose fin located behind the dorsal fin in front of the caudal fin. This pacu fish is the largest representative of this suborder in South American waters. With its tall, laterally compressed body, it resembles an ordinary piranha. However, it is well distinguished by color: the body is painted in shades of black and gray, so it has another name - black pacu. This large fish has large eyes, in which you can notice curiosity about everything that is around.
The usual size that most fish of the species Colossoma macropomum reach in nature is about 70 centimeters. The maximum recorded body length is 108 centimeters, and published data indicate the greatest weight - 40 kilograms. The brown pacu has 10 percent body fat (a fairly high figure), has tasty meat and is an object of fish farming. These fish with good immunity were introduced into many large rivers in tropical America and even into the rivers of Southeast Asia to be raised for food.
Nutrition and lifestyle
Herbivorous pacu fish are often called fish with “human teeth”. Their teeth bear a vague resemblance to human molars. Therefore, they very easily eat grain crops, fruits and nuts, and plant debris that they find in the water. The brown pacu is no exception; at the same time, it can also eat small fish, insects and invertebrates.
The diet of young individuals consists of zooplankton, snails and insects. And only with age do fish switch to a preferably plant-based diet.
The brown pacu probably breeds during river floods and in flooded floodplain forests. The fishbase website reports that juveniles and “teenagers” live in the black waters of the floodplains until they reach sexual maturity. And adult specimens remain in flooded forests for five months after the flood, and then, apparently, return to the rivers.
The black pacu leads a solitary lifestyle, and this differs from the natterer piranha.
The difficulty in maintaining any pacu is the need to purchase a sufficiently large tank, which can weigh about one ton. In such an aquarium it is necessary to install powerful filters that will maintain high water quality. The heater should maintain warm water in the aquarium (about 26-28 C), an aerator and lamps for lighting are also needed.
In the photo of the red pacu fish, the decorations of the aquarium are slightly visible - large rocks. Large driftwood can also be placed. It is better to use only artificial plants for decorative purposes; any living plants will be eaten by fish.
The pacu's diet in the aquarium should be balanced. The approximate composition of a serving may look like this - small pieces of vegetables and fruits (apple, cabbage or zucchini), combined with meat (shellfish or shrimp).
Favorite by many lovers aquarium fish Pacu is a real exotic. By mistake, this beauty from South America is considered one of the bloodthirsty fish. And the reason for this is that it belongs to the wide subfamily of Piranha fish, about which real legends are formed. Actually this is not true. Of all known species of this subfamily, only 43% are aggressive predators. The remaining 57% can safely be called semi-predators, who feed mainly on plant foods.
It is precisely for vegetarians that our Paku fish, which first came to our continent more than 200 years ago. It appeared in domestic aquariums at the end of the last century and in a short time managed to become a real favorite of aquarists. The natural habitat of this species is the Amazon River delta and adjacent reservoirs. Due to its large size and rapid growth, the fish is considered a commercial fish.
Description and types of Paku fish
Only a few species of these fish are most widespread among aquarists:
- Red Pacu (Piaractus Brachypomus) or two-toothed colossoma;
- Brown Paku; (Colossoma macropomum).
Red Pacu fish photo, which can be viewed on this page, has a flat body, painted in a characteristic color scheme. Almost its entire surface is covered with silvery scales. Only the pectoral fins and the abdomen with the anal fin have a red tint. The caudal fin of the fish is edged with a dark stripe.
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Living in the natural environment (Amazon and Orinoco rivers), Red Pacu fish can reach a length of up to 1 meter. At the same time, the weight of one such adult individual can reach up to 25 kilograms. In aquarium conditions, fish grow up to 40-60 cm in length. Which requires an appropriate aquarium volume.
Brown Paku The body shape is not much different from the red one. It is also compressed on the sides and has an impressive height. But its coloring, as you already understood from the name of the species, is completely different. It can be in different variations, from black to silver-gray. At the same time, the abdomen and pectoral fins of adult individuals have a brownish-bronze tint.
In terms of its size, the brown-colored Paku is a large fish. In terms of length and body weight, it is one and a half times greater than its red relative. Fishermen in the Amazon managed to catch individuals that were more than one meter in length. And their weight reached 40 kilograms. However, as home-keeping practice shows, representatives of this species do not grow more than 60 centimeters in an aquarium.
Choosing an aquarium for Paku fish
When planning to purchase one or another type of Paku, it is very important not to miss the size of the fish aquarium. A huge role in determining the volume of a home reservoir for keeping these exotics is played by such criteria as:
- Fast growth of fish;
- Lifestyle.
As we mentioned above, individuals of this species grow very quickly. In just three months, young Paku fish measuring 3-4 centimeters in size grow to 28 centimeter giants. And their growth doesn’t stop there. By the age of one year, they gain weight up to 4 kg and reach and increase in their linear dimensions up to 40 cm. Thus, for comfortable maintenance of one individual, at least 100 liters will be required.
According to your lifestyle Red Paku, however, like Brown, refers to schooling fish. Even if we take 4 representatives of the subfamily, the minimum volume for an aquarium will be 400 liters. But for more comfortable maintenance, you will need a reservoir of 700 liters or more.
When the volume of the aquarium has been selected based on the number of fish, it’s time to clarify the situation with its dimensions. Due to the large size of Pacu fish and their rapid growth, it makes no sense to use short containers. The optimal length from which to base your selection in this case would be an aquarium of 1.2 meters or more. Width also plays a significant role. Fish need room to maneuver freely. Therefore, the width should be at least 60-70 centimeters. The height of the home pond should not be less than 60 cm.
As we mentioned above, a minimum of 1 cubic meter of water is required to maintain one Paku individual. It is very important to observe the following parameters:
- Comfortable temperature - 22 o C28 o C;
- Hardness range - 5 o 20 o;
- The acidity of the medium is pH 6-7 units.
But this is not entirely enough. The fish will need to be provided with water, for which an internal and external filter is installed. A prerequisite for comfortable keeping Paku fish in the aquarium is the presence of an aerator that saturates the water with oxygen. And, of course, you need to change the water weekly by 1/3 of the total volume of the aquarium.
It is best to line the bottom of the aquarium with coarse gravel. Having a small one will cause certain difficulties when caring for pets. It is very difficult to clean it from fish waste products.
Caring for Paku fish The video we invite you to watch involves planting a small amount of vegetation. There shouldn’t be a lot of it, as it will be eaten anyway. It is better to replace the main part of the vegetation with artificial plants. This will create a more comfortable atmosphere for large people. And in order for the fish to feel protected, decorative caves and grottoes can be placed in the aquarium, allowing them to hide.
Feeding the Paku fish
Red and Brown Pacu have excellent appetites, so feeding them should be regular and not excessive. It is fashionable to give plant food to fish as food. As fans note, piranha-like pets eagerly eat chopped lettuce, dandelions, and cabbage. They also love to eat fruit.
In addition to plant foods, you can also give live food. Here it is appropriate to give fish, tubifex, and earthworms. Paku's teeth allow fish to cope with meat. Some aquarists practice feeding minced meat. However, food of animal origin should not be abused. It is best used as an occasional addition to plant foods. If you feed meat on a regular basis, your fish may develop aggressive behavior.
Breeding in a home aquarium
Paku fish reach sexual maturity at the age of one to two years. However, at home, these fish reproduce with difficulty. It is very difficult to find any useful and specific information on this matter. This is what we managed to find out from experienced aquarists.
Breeding piranha fish of the Paku species must be approached thoroughly. It is very important to adhere to certain criteria:
- Aquarium volume;
- Abundant and varied feeding;
- Superior numbers of males.
When choosing a spawning tank for producers, its volume is very important. It should not be less than 300 liters. After its disinfection, they begin to prepare the producers themselves. To stimulate spawning, you will have to resort to pituitary injections. After which the Paku fish begin to be fed intensively. The Paku's diet should be varied with a predominance of animal proteins.
After the producers are ready to reproduce, males and females are placed in the spawning tank. In this case, the number of the former should exceed the number of females. As a rule, after spawning, parents forget about their offspring. And therefore they can be safely placed in a common aquarium. In order for the fry to grow intensively, they must be fed abundantly. Artemia will be used as food for little Pacu. As the juveniles grow, they need to be sorted. If this is not done, the larger ones will eat the smaller ones.
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