The Black Pacu (Tambaqui) is a massive, incredibly fast-growing Amazonian fish. Closely related to Piranhas, they possess crushing, human-like teeth evolved for cracking nuts and seeds. Due to their enormous adult size (often exceeding 3 feet and 60 lbs) and extreme bioload, they are completely unsuitable for standard home aquariums and require colossal custom tanks or heated indoor ponds.
At a Glance
Tank Requirements
Water Parameters
Temperament & Compatibility
Available Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard / Adult
The fully grown adult form. Requires a massive custom aquarium or pond. They will decimate live plants, rearrange decor, and can easily shatter glass heaters or thin acrylic with their powerful jaws and sheer mass.
Same care requirements as the base species
Also known as: Adult Pacu, Monster Pacu
Juvenile (Grow-out)
Juveniles are commonly sold in the trade at 2-3 inches, often mistaken for Piranhas. They grow at an explosive rate (up to an inch per month in their first year) and will rapidly outgrow any standard starter aquarium.
Differs in 3 traits from base species
Also known as: Baby Pacu, Dwarf Pacu
Black Pacu Care Guide Summary
The Black Pacu, scientifically known as Colossoma macropomum, belongs to the Characins family group. Adults reach a maximum size of approximately 90 cm and have a compressed body shape with a fast growth rate. Classified as mostly peaceful, this species primarily occupies the mid-level and bottom zones of the aquarium and produces a extreme level of biological waste.
To thrive, the Black Pacu requires a freshwater only aquarium with a minimum volume of 3800 litres and a tank length of at least 300 cm. Water temperature should be maintained between 22°C and 28°C, with a pH range of 6–7.5 and a general hardness of 2–15 dGH. A moderate water flow is preferred.
The Black Pacu is a rewarding species to keep, provided its core environmental needs are met. This species is available in 2 varieties: Standard / Adult and Juvenile (Grow-out). Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Black Pacu Habitat Setup
When setting up an aquarium for the Black Pacu, a moderate water flow best suits their natural preferences. Because this species occupies the mid-level and bottom zones, the aquarium layout should prioritise open swimming space in the centre of the tank for free movement and sufficient floor space with hiding spots among rocks, wood, or dense planting. Useful additions include smooth gravel or rounded substrate to protect their sensitive barbels and driftwood, which can serve as both a hiding place and a dietary supplement. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper and live planted layouts may be difficult to maintain, as this species tends to uproot or consume vegetation.
Black Pacu Compatibility Notes
Classified as mostly peaceful, the Black Pacu is adaptable and can be kept singly or in a small group, offering flexibility when planning a community tank. When choosing tankmates, shy or slow-feeding tankmates may be outcompeted at feeding time and their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the mid-level and bottom zones can help reduce competition and territorial overlap.
Black Pacu Feeding & Diet Considerations
The Black Pacu will eat fry, so breeding efforts in the same tank are unlikely to succeed and is an aggressive eater that may prevent timid tankmates from getting enough food — target feeding or simultaneous feeding at opposite ends of the tank can help.
Frequently Asked Questions About Black Pacu
How big does Black Pacu get?+
What tank size does Black Pacu need?+
What water parameters does Black Pacu need?+
Is Black Pacu peaceful or aggressive?+
Can Black Pacu live alone?+
Does Black Pacu have any special tank requirements?+
Does Black Pacu need a lid on the tank?+
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