Pacu

Quick facts

Adult size

70 cm, 3500 g typical harvest weight

Days to harvest

365 to 730 days from fingerling

Lifespan (max)

up to 25 years

Diet

omnivore

Temperature class

warm-water

Difficulty

intermediate

Water parameters

Temperature range

22–32°C (optimum 27°C)

pH

5.5 to 7.5

Hardness

2 to 20 dGH

Minimum tank

2000 L per individual at harvest size

Feed and growth

Feed protein

28% target

Daily feed (warm water)

1.20% of body weight per day

Daily feed (cool water)

0.50% of body weight per day

Max stocking density

35 g per litre of system water

A 3500g adult eats about 42.0 g of feed per day at optimum temperature. For a roster of 10 fish at adult size, that's around 420 g of feed daily.

Legality

Aquaculture and possession rules vary by jurisdiction and change over time. This table reflects regulations as of the verified date on each row. Verify with your local fisheries or wildlife authority before stocking.

Jurisdictions not listed here default to "check local regulations". A non-listing is not a green light; rules in your specific county or municipality may apply.

Habitat and origin

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 classification

tropical (needs warm water year-round)

Outdoor pond zones (USDA)

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

Heating in a temperate climate

Required for year-round operation

Cooling in a temperate climate

Not required

Zone bounds reflect year-round outdoor pond viability with no active heating. Anywhere outside the bounded zone, the species can still be kept in an indoor heated tank or a seasonally-managed system. Verify your specific microclimate, as a sheltered yard zone can run a half-zone warmer than the regional rating.

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