Pacu
Also known as: Colossoma macropomum
The Pacu (Colossoma macropomum) is a large freshwater fish native to the Amazon Basin, closely related to piranhas but distinguished by its human-like molar teeth adapted for crushing nuts and fruits. The Pacu originates from Amazon River basin in South America, including Brazil, Peru, Colombia, Venezuela, and Bolivia, reaches Adult size: 80-100 cm in captivity, typically lives 15-25 years, and is kept at 24-28°C (75-82°F). Individual fish vary, so treat this as a general guide rather than a guarantee.
Species at a glance
- Origin
- Amazon River basin in South America, including Brazil, Peru, Colombia, Venezuela, and Bolivia
- Adult size
- Adult size: 80-100 cm (31-39 inches)
- Life span
- 15-25 years
- Temperament
- Generally peaceful but can become territorial and aggressive as they mature, especially in confined spaces
- Tank size
- Minimum 1000 liters (264 gallons) for a single adult; 1500+ liters (396+ gallons) recommended for long-term health
- Water temp
- 24-28°C (75-82°F)
- pH range
- 6.0-7.5
- Diet
- Omnivorous; primarily fruits, nuts, seeds, and aquatic plants in the wild; in captivity, accept high-quality pellets, vegetables (lettuce, zucchini, spinach), fruits (apple, banana, melon), and occasional protein sources like shrimp or earthworms
- Other names
- Colossoma macropomum
About the Pacu
The Pacu (Colossoma macropomum) is a large freshwater fish native to the Amazon Basin, closely related to piranhas but distinguished by its human-like molar teeth adapted for crushing nuts and fruits. It can grow over 1 meter in length and weigh up to 40 kg in the wild, making it one of the largest characins. Juveniles are often mistaken for piranhas due to similar appearance, but adults develop a deep, laterally compressed body with silvery scales and a distinctive hump behind the head. Pacus are important in their ecosystem as seed dispersers and are also farmed commercially for food in South America.
Lifespan and health
With optimal care, Pacus commonly live 15-25 years in captivity, though exceptional individuals may reach 30 years. Lifespan is heavily influenced by tank size, diet quality, and water stability—fish kept in undersized tanks (<750L) or fed excessive protein often develop health issues by age 5-8 and rarely exceed 10 years. Regular monitoring of growth rate is essential; healthy juveniles should gain 2-3 cm per month in the first year, slowing to 1-2 cm annually after maturity. Common health issues include obesity from overfeeding (evident as distended abdomen and lethargy), which can lead to fatty liver disease and reduced lifespan. Hole-in-the-head disease (HLLE) may occur due to poor water quality or nutritional deficiencies, particularly lack of vitamins C and D; prevent with varied diet and frequent water changes. Fin rot and bacterial infections are rare but possible if tank hygiene is neglected—treat promptly with antibiotics if signs appear. Parasitic infections like ich are uncommon in well-maintained tanks but can arise from new fish introductions; quarantine all new additions for 4-6 weeks.
Overview
The Pacu (Colossoma macropomum) is a large freshwater fish native to the Amazon Basin, closely related to piranhas but distinguished by its human-like molar teeth adapted for crushing nuts and fruits. It can grow over 1 meter in length and weigh up to 40 kg in the wild, making it one of the largest characins. Juveniles are often mistaken for piranhas due to similar appearance, but adults develop a deep, laterally compressed body with silvery scales and a distinctive hump behind the head. Pacus are important in their ecosystem as seed dispersers and are also farmed commercially for food in South America.
Care and tank setup
Tank setup requires a minimum of 1000 liters (264 gallons) for a single adult, with strong filtration (canister or sump system rated for 2x tank volume) to handle their high waste production. Use a sandy substrate and provide driftwood or rock structures for hiding, but avoid sharp decorations that could injure their large bodies. Ensure the tank has a secure lid as Pacus are known to jump when startled or stressed. Water parameters must be maintained with weekly 25-30% water changes; ammonia and nitrite should remain at 0 ppm, nitrate below 20 ppm. Temperature stability is critical—use a reliable heater and thermometer to keep within 24-28°C (75-82°F). Feed a varied diet 2-3 times daily, offering only what they can consume in 2-3 minutes; overfeeding leads to obesity and water quality issues. Include blanched vegetables daily and supplement with spirulina-based pellets. Avoid housing with small fish (under 15 cm) as they may be seen as prey; suitable tankmates include other large, peaceful species like Oscar fish, Silver Dollars, or large Plecos, but monitor for aggression as Pacus mature.
Related breeds
Breed information on this page is based on the Wikipedia article on the Pacu, supplemented with additional research. Reviewed for accuracy.