Pacu

Water parameters

Minimum tank: 2000 L per individual at harvest size.

Feed and growth

Feed protein

28% target

Daily feed (warm)

1.20% of body weight

Daily feed (cool)

0.50% of body weight

Max density

35 g per litre

A 3500 g adult eats about 42.0 g of feed per day at optimum. 10 fish at adult size: ~420 g daily.

Legality

Rules vary by jurisdiction and change over time. Verify with your local fisheries or wildlife authority before stocking.

Unlisted jurisdictions default to "check local regulations".

Origin and habitat

A group of several related species in the family Serrasalmidae (the piranha family), native to South American rivers, particularly the Amazon and Orinoco basins. The most commonly cultured species are Colossoma macropomum (tambaqui, also called black pacu) and Piaractus brachypomus (red-bellied pacu or pirapitinga). Pacu are large, round-bodied, herbivorous to omnivorous fish that feed on fruits, seeds, nuts, and plant material in the wild. Adults reach 70–100 cm and 20–40 kg. Pacu are important aquaculture species across South America and have been introduced to tropical regions worldwide for food production. The flesh is firm, mild, and somewhat fatty, considered excellent eating in Brazil and neighboring countries.

Climate and outdoor ponds

Climate

tropical (needs warm water year-round)

USDA zones

10–13 (winter low around -1°C or warmer)

Heating needed

yes

Cooling needed

no

Care notes

A warm-water food fish for tropical aquaponics systems, particularly suited to South American and tropical Asian contexts. Optimal temperature is 25–30°C; below 18°C they stop eating, below 12°C they die. Growth is fast in warm conditions: 500–1.5 g in 8-12 months on commercial pellet (28-35% protein). FCR is 1.3-1.8, excellent for a species that can reach 20 kg given time. The herbivorous to omnivorous feeding habit is a strong advantage for integrated aquaponics: pacu readily eat plant material, fruits, seeds, vegetable scraps, duckweed, and excess plant biomass from the grow beds, reducing pelleted feed costs by 20-40% in well-managed systems. Stocking density: 15-30 g/L. Pacu tolerate moderate water quality conditions (DO above 3 mg/L, wide pH range, moderate ammonia tolerance). They're schooling fish that do best in groups of 3+. The main concern outside South America is that pacu grow very large and require substantial tank volume for adults (though most aquaponics operators harvest at 1–2 kg, well before maximum size). Pacu are regulated in some US states as potentially invasive tropical species; check local regulations. In several US states, pacu culture is legal with permits. In Brazil, pacu (particularly tambaqui, Colossoma macropomum) aquaculture is a multi-billion-dollar industry. Fingerlings are available from tropical fish hatcheries in South America and from some US suppliers in Florida, Hawaii, and Puerto Rico.

Further reading

• Aquaponics water chemistry: balancing pH for fish and plants
• Fish for aquaponics: tilapia vs everything else