Red-Bellied Pacu (Piaractus brachypomus)

One quantity buys one live, unsexed Red-Bellied Pacu in the size selected above. This is not a pair, group or ten-pack. Available size choices and current stock are shown in the selector. The fish supplied is a juvenile; its small dispatch size must not be confused with its adult requirements.

The Red-Bellied Pacu, Piaractus brachypomus, is also sold under the names Pirapitinga and Freshwater Pompano. It is a giant South American freshwater fish from the pacu and piranha family, Serrasalmidae. Juveniles have a silver, laterally compressed body with darker upper colour and a red to orange chest and belly. Their calm-looking appearance and manageable juvenile size can conceal the most important fact about this species: the USGS reports a maximum of 85 cm standard length and 20 kg, while FishBase separately records 88 cm total length and 25 kg. These are distinct published maxima measured or reported by different sources, not a single 20-25 kg adult-weight range.

This is specialist, custom-system livestock, not a normal community-aquarium fish. An adult needs heated housing with a footprint measured in metres, filtration designed for a very large-bodied animal and a realistic multi-decade care plan. The RSPCA specifically names pacu among fishes that can grow so large that they may be unsuitable as pets. Please do not order a juvenile unless the adult facility, maintenance budget and responsible rehoming contingency have already been considered.

Red-Bellied Pacu at a glance

Identity, taxonomy and natural range

Piaractus brachypomus is a characiform fish in the family Serrasalmidae. Pacus, piranhas and silver dollars sit within this broader family, but those common groupings do not make them interchangeable aquarium animals. Red-Bellied Pacu possess broad, molar-like crushing teeth suited to processing bulky foods. The teeth differ from the sharper cutting dentition associated with piranhas, yet a large pacu still has a powerful jaw and can inflict a serious bite.

The product's supplier provenance uses the older combination Colossoma brachypomum, while the accepted name is Piaractus brachypomus. Both names are presented here so older catalogues and trade labels can be understood without obscuring the accepted identity. "Pirapitinga" and "Freshwater Pompano" are established common names for the same sold entity; they are aliases, not separate variants or colour forms.

Modern taxonomic evidence places P. brachypomus in the Amazon basin. Older references often state that it also occurs naturally in the Orinoco. A 2019 peer-reviewed redescription separated the Orinoco fish as Piaractus orinoquensis and restricted P. brachypomus to the Amazon basin. This page follows that newer interpretation instead of repeating the outdated combined range.

Amazon floodplains and seasonally inundated forest are central to the species' ecology. Wild pacu exploit plant material, fruits and seeds when flooded forest makes those resources available, while other recorded foods include insects and decaying plant matter. That ecology explains the fish's robust crushing dentition and plant-led feeding style, but it should not be copied literally by offering whole hard nuts or unlimited sugary fruit in an aquarium. Captive food must be safe, nutritionally complete and manageable for water quality.

Why juvenile size is misleading

A juvenile Red-Bellied Pacu can fit comfortably into a dealer aquarium and may initially resemble a much smaller community fish. It grows into a deep-bodied animal whose published maximum is close to a metre. FishBase records 88 cm total length and 25 kg, while the USGS profile reports 85 cm standard length and 20 kg. Standard length excludes the tail fin and total length includes it, so these figures describe different measurements rather than a contradiction.

Growth rate is not a safe basis for delaying the adult plan. Food, temperature, genetics, stocking and water quality can alter how quickly an individual grows, but keeping it cramped does not create a healthy small adult. Stunting is not responsible size control. The correct question before purchase is not how long a small tank might last; it is where the fish will live when its body depth, turning radius, waste production and physical strength exceed ordinary aquarium capacity.

The selected variant describes the approximate dispatch size, not a promised exact measurement on arrival. Live fish vary naturally and may be measured at slightly different points by suppliers. Sex is not guaranteed. Juveniles cannot be reliably sexed from ordinary external appearance, and the product is not offered as a male, female, pair or breeding group.

Adult accommodation: a custom facility, not a standard tank

There is no defensible universal litre figure that makes an adult pacu setup suitable by itself. Volume can conceal a tank that is tall but too narrow for the fish to turn, or a long tank with inadequate filtration and maintenance access.

For one adult, think in terms of a custom aquarium, indoor pond or professionally engineered aquatic enclosure with straight-line swimming room and enough front-to-back depth for an unhurried full turn. As a cautious planning starting point, Tropical Fish Co would discuss a footprint around 3 m long and approximately 1.2 m front-to-back, with water volume in the several-thousand-litre range. This is an informed planning inference from published adult dimensions, not a published biological minimum or a guarantee that every system at those dimensions is adequate. A larger footprint is preferable, and the animal's actual condition, structure, filtration, oxygenation and maintenance regime may demand substantially more.

The complete adult system should exist or be contractually and financially realistic before a juvenile is bought. A temporary grow-out aquarium is only acceptable as one stage of a written upgrade plan. Doorways, floor loading, drainage, power supply, heating redundancy and safe access for maintenance all become serious design constraints at this scale. Consultation with an experienced large-fish facility, aquarium engineer and appropriately qualified structural professional may be needed.

Footprint and interior layout

• Prioritise length and front-to-back turning width over decorative height.
• Keep a broad, continuous swimming lane rather than filling the footprint with rockwork.
• Use securely fixed, rounded structures that cannot shift when struck by a powerful fish.
• Avoid sharp stone, narrow gaps, exposed heater glass and abrasive fittings.
• Provide visual shelter at one end without creating a trap or blind collision point.
• Use a secure cover or containment design; a startled pacu can jump or hit lids with force.
• Choose a smooth sand or rounded fine substrate, or an easy-clean specialist base suited to the filtration plan.

Planted displays are difficult. Pacu may browse, tear or uproot vegetation, and unsecured pots can become impact hazards. Tough plants fixed outside the main swimming path may persist, but the fish's welfare takes priority over an elaborate aquascape. Moderate lighting with a predictable day-night cycle is practical. A shaded end or broken sight line can help a new juvenile settle, while sudden lights and movement should be avoided.

Heating, oxygen and fail-safe design

For a small dispatched juvenile, use a stable routine temperature of 27-28°C unless the fish's known source conditions and a qualified fish-health professional require a different acclimation plan. FishBase records 23-28°C as an environmental range, but that is not the same as a captive recommendation. A controlled study of early juveniles found that 24°C reduced growth performance relative to 28°C, while its literature review reports 27°C as the best growth temperature. In a large UK installation, heating capacity, insulation and redundancy matter as much as the chosen set point. Use protected heating equipment that the fish cannot contact or break. An alarm for temperature or power failure and a contingency for prolonged outages are sensible because many hundreds or thousands of litres cannot be corrected quickly after a system failure.

High dissolved oxygen and active surface movement are important, especially at warm temperatures and after feeding. A backup air pump or generator plan should match the value and welfare risk of the animal. Pumps, returns and overflows need guards strong enough to prevent access while still allowing routine cleaning. Every component must be serviceable without leaving the fish in deteriorating water.

Filtration and water quality

Adult pacu create a very heavy organic load. Filtration should be designed around the projected adult biomass and feeding regime, not the juvenile's current size or a pump's marketing label. A large sump or similarly accessible system can combine mechanical capture, biological media, aeration and safe equipment placement. Multiple circuits add resilience and allow one section to be serviced without removing all circulation.

Mechanical waste should be captured where it can be removed frequently. Allowing vegetable fragments and faeces to decay in inaccessible media raises oxygen demand and dissolved waste. Biological capacity must be mature before the fish enters the system. Ammonia and nitrite should remain undetectable on a reliable test, while nitrate and other dissolved waste should be controlled through measured feeding, cleaning and water changes appropriate to the installation.

Do not "cycle for four to six weeks" by the calendar and assume the system is ready. Cycling is complete when the filter demonstrably processes the expected ammonia load and repeat tests show stable zero ammonia and zero nitrite. A giant-fish system needs a planned source of conditioned replacement water, safe temperature matching and drainage that makes large water changes routine rather than exceptional.

Published environmental records include 23-28°C, pH 4.8-6.8 and hardness up to 15 dH. Wild database values are not instructions to force a newly purchased fish into acidic or cool water. For captive planning, approximately pH 6.0-7.5 and 5-15 dGH can be workable when the water is stable, clean and close to the fish's conditioned source water. Avoid abrupt pH, hardness or temperature changes. Our aquarium water chemistry guide explains pH, GH, KH, ammonia, nitrite and nitrate in more detail.

Feeding a Red-Bellied Pacu

Red-Bellied Pacu are best treated as plant-led omnivores. Wild feeding studies document fruit and seed consumption in flooded forest, and biological summaries also record insects and plant material. A captive diet should translate that nutritional pattern into safe, controlled foods rather than attempting to recreate the river by adding whole nuts, large seeds or unlimited fruit.

Use a reputable, size-appropriate formulated pellet for large herbivorous or omnivorous freshwater fish as the nutritional foundation. Supplement it with varied leafy greens and suitable vegetables such as courgette, peas or other soft, clean plant material. Introduce unfamiliar foods gradually. Fruit can be offered only occasionally and in small portions because sugar and soft debris can add unnecessary calories and rapidly foul warm water.

Occasional animal protein may be accepted, but a meat-heavy routine, feeder fish and fatty processed foods are inappropriate. Feeder fish add avoidable disease and injury risk and do not reflect the plant-led plan. Never offer salted, seasoned or processed human food. Whole hard nuts or stones from fruit can create a choking, dental or obstruction hazard and should not be used simply because wild pacu consume seeds.

Portion and observation

Feed an amount the fish consumes cleanly while it remains calm and balanced. Juveniles may need smaller meals more often than adults, but appetite alone is not a portion guide; pacu can be highly food-responsive. Remove uneaten vegetables before they soften and break apart. Adjust feeding against body condition, growth, temperature, activity and measured water quality rather than following a fixed number of minutes regardless of food type.

• Watch the complete feeding response rather than throwing food in and leaving.
• Spread floating or sinking items so the fish does not repeatedly strike one hard surface.
• Keep hands out of the feeding zone; use suitable tongs or another controlled method.
• Record appetite changes, rejected food and unusual waste because these can be early warning signs.
• Reduce the portion and test water when leftovers, cloudiness or rising nitrate show that the system is being overloaded.

A suddenly reduced appetite can reflect stress, poor water, temperature change, injury or illness. Do not hide the symptom by offering richer and richer treats. Check water and equipment first, then seek advice from an aquatic veterinarian or experienced fish-health professional when the cause remains uncertain.

Behaviour, social needs and handling safety

A settled pacu is often alert, non-territorial and strongly responsive to routine. Juveniles may use loose grouping behaviour in nature, but that does not make a ten-fish home purchase appropriate. The space needed by multiple adults increases far beyond the reach of an ordinary private aquarium, and the waste and collision risk multiply with each animal.

For most private keepers, one Red-Bellied Pacu is the realistic plan. Keeping several should be considered only by an institution-scale facility able to provide the resulting adult footprint, filtration capacity and welfare monitoring. This listing therefore sells one fish per quantity and should not be interpreted as recommending a shoal.

Pacu can startle at sudden movement, impact noise, abrupt lighting or unfamiliar work around the enclosure. A frightened adult has enough mass to injure itself against glass or decor and enough strength to dislodge equipment. Approach predictably, keep clear turning space and avoid chasing it around the system. Any capture, transport or treatment plan for an adult should be developed with experienced large-fish handlers before it is needed.

Although the species is usually described as peaceful, peaceful does not mean harmless. The crushing teeth and powerful jaw can cause a serious bite. Do not hand-feed, put fingers near the mouth or encourage the fish to associate hands with food. Children and visitors should not be able to open the enclosure or reach the water unsupervised.

Tank mates and compatibility

This is not a conventional community fish. Small fish, shrimp and other bite-sized livestock are unsuitable and may be eaten or injured even when the pacu is not an active predator. Delicate or slow animals can be struck by a startled fish. Territorial cichlids and fin-nipping species may provoke panic or cause persistent damage.

Very large, calm catfish or other robust fish are sometimes kept with pacu in public displays, but a species name alone cannot establish compatibility. Every additional animal changes adult space, filtration, feeding, disease and escape-management requirements. Different feeding speeds, nocturnal activity, armour, spines and aggression must all be assessed. A companion that looks similar in size at purchase may be dangerously mismatched after growth.

A single-specimen, species-focused installation is usually the clearest private-care plan. If a mixed giant-fish display is proposed, it should be designed around the adult dimensions and behaviour of every species, with an immediate separation option. Browse our other freshwater fish only for comparison; the category is not a list of automatic pacu tank mates.

Appearance and how it changes with age

Juveniles are silver with a dark upper body and a warm red or orange wash beneath. That pattern can make them resemble juvenile red-bellied piranhas at a glance. The deeper head profile and broad crushing teeth help distinguish pacu, but teeth should never be inspected by handling a live fish. Identity should come from reliable supplier provenance and taxonomic checks, not appearance alone.

As the fish matures, body depth and head mass become much more pronounced. The bright juvenile underside can soften or become less dominant with age. Colour intensity is affected by age, individual variation, lighting, surroundings, diet, stress and camera processing, so an exact red shade is not guaranteed.

The four gallery images are representative illustrations based on a supplier reference. They help show juvenile form and colour but are not photographs of the exact fish that will be dispatched. One image depicts two fish to show body shape from more than one angle; it does not change the sale unit. One quantity still buys one fish.

Sexing and breeding

Juvenile sex is not reliably determined from ordinary external appearance, and no sex is promised. Mature females may look fuller when carrying eggs, but body shape alone is not a dependable retail sexing method. Do not buy two juveniles expecting a guaranteed pair.

Red-Bellied Pacu breeding is not a normal home-aquarium project. Commercial aquaculture uses very large facilities and specialised reproductive management. Seasonal flood cues, adult body size, uncertain sexing and the need to manage eggs and rapidly growing young put responsible breeding beyond a standard domestic setup.

Anyone with a legitimate propagation objective should work from peer-reviewed aquaculture protocols, legal requirements and appropriately qualified professional support rather than improvising hormone use or pond-scale spawning.

Arrival, acclimation and quarantine

Prepare and test the destination before dispatch. The system must be mature, heated, covered and matched closely enough to the source water that acclimation does not require a sudden chemical change. Confirm that pumps, heaters, guards and backup aeration work under load. Do not order first and attempt to cycle or redesign the aquarium while the fish is in transit.

On arrival, inspect the sealed bag and fish before opening. Follow the current instructions supplied with the order and our fish acclimation guide. Temperature equalisation and water adjustment should be controlled, but prolonged bag opening can allow accumulated waste chemistry to become more harmful. Never pour transport water into the established system.

Quarantine is strongly advised before any mixed display. The quarantine enclosure must still permit safe movement for the size received and must have mature biological filtration, secure heat and cover. Observe respiration, balance, appetite, skin, eyes, fins and waste. Test ammonia and nitrite frequently, particularly after the first meals.

There is no universal calendar that proves a fish is disease-free. A two-to-four-week observation period is commonly used in ornamental fishkeeping, but duration should respond to symptoms, source history, diagnosis and professional advice. Do not medicate routinely without a reason. Treatments can stress fish, damage filtration or become unsafe when used at the wrong dose or against the wrong condition.

Health monitoring and prevention

A healthy juvenile should be balanced in the water, breathe without persistent distress, respond to its surroundings and accept appropriate food after settling. Normal caution on arrival is different from repeated crashing, rolling, gasping, clamped fins, excess mucus, ulcers, white spots or progressive appetite loss.

Many apparent "diseases" begin with environment. Test temperature, ammonia, nitrite, pH trend and equipment before reaching for medication. Check for collision hazards and bullying. Record results, take clear photographs where useful and seek aquatic veterinary guidance for persistent or serious signs. A large display system should have a treatment and isolation plan before an adult becomes too heavy to move safely.

Common preventable risks

• Ammonia or nitrite exposure: immature filtration, overfeeding or a failed pump can create an emergency quickly.
• Collision injury: cramped layouts, sharp decor and sudden disturbance can damage the snout, eyes, fins or body.
• Chronic poor water: rising dissolved waste can suppress appetite, condition and resistance to infection.
• Diet imbalance: rich, repetitive food can promote excess fat, digestive trouble and severe water fouling.
• Thermal failure: underpowered or unprotected heating and a lack of backup planning can expose a tropical giant to rapid stress.
• Unsafe handling: the fish's mass, teeth and panic response can injure both fish and keeper.

Water changes should be regular enough that test trends remain controlled rather than delayed until the water looks dirty. Clean mechanical stages before trapped material decays, but preserve biological media and avoid replacing every filter component at once. Keep a maintenance log because gradual deterioration is easier to see in numbers than by looking through a very large volume of water.

Long-term responsibility and rehoming

FishBase records a maximum reported age of 28 years. That does not promise that every captive fish will live exactly that long, but it makes a multi-decade commitment plausible. Housing, power, water, food, equipment replacement, structural needs and veterinary access can cost far more than the juvenile purchase.

Before ordering, identify who will care for the fish through a house move, illness, power outage or change in circumstances. Public aquariums and specialist keepers have limited capacity and cannot be assumed to accept an unwanted giant fish. Contact a potential rehoming route early, disclose the exact identity and measured size, and verify the receiving system before any transfer.

Never release a pacu into a river, lake, canal or outdoor pond connected to natural water. UK government guidance warns that ornamental fish can spread disease, harm ecosystems and breach controls on moving or releasing fish. If continued care becomes impossible, speak to an experienced aquatic retailer, fish-health professional, suitable licensed facility or specialist rehoming network. The receiver must understand the adult size and complete care requirement.

Is this the right fish for you?

A Red-Bellied Pacu can become an impressive, intelligent-looking centrepiece in a properly engineered giant-fish facility. Its appeal comes from its deep body, strong feeding response, Amazon floodplain ecology and dramatic growth. Those same qualities make it unsuitable for most aquariums.

This fish may be appropriate only when all of the following are already true:

• You understand that the selected juvenile can reach 85 cm standard length by one published record or 88 cm total length by another.
• You have a credible adult facility measured in metres and several thousand litres, not merely a temporary tank.
• The floor, electrical supply, drainage, heating, filtration and emergency aeration are designed for the installation.
• You intend to keep one specimen unless operating an institution-scale system assessed for a group.
• You can fund a plant-led diet, large water changes, equipment replacement and professional help over multiple decades.
• You accept that the fish is unsexed and the gallery is representative rather than an exact specimen promise.
• You have a responsible contingency that never depends on release into the wild.

If any point is uncertain, delay the purchase and design the adult system first. Our broader freshwater fish collection includes species with far more manageable adult requirements. For current livestock packing, eligibility and Live Arrival Guarantee terms, read the delivery information before ordering.

Evidence used for this care guide

This guide uses the FishBase species record for accepted identity, environmental records, maximum total length, weight and age; the USGS species profile for identification and maximum standard length; the 2019 peer-reviewed taxonomic redescription for the Amazon-versus-Orinoco split; controlled juvenile temperature research; peer-reviewed floodplain feeding research; the RSPCA aquarium guidance for adult-size welfare context; and current UK government guidance on keeping, moving and never releasing non-native ornamental fish. Aquarium dimensions are labelled as a conservative planning inference because the reviewed biological sources do not publish a universal lifelong tank minimum for this giant species.