Red-bellied Pacu
Piaractus brachypomus
Serrasalmidae
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About
The red-bellied pacu is a serrasalmid — a piranha relative that traded cutting teeth for flat molars and lives on fruit, nuts and seeds. Shops sell it at 5-8 cm as a silver coin with a red throat, and it is routinely mislabelled: Seriously Fish notes it is offered as a 'vegetarian piranha', and Lithuanian shops list it flatly as Piranija. FishBase records the wild adult at 88 cm and 25 kg. This is the fish behind most of the 'piranha found in a European lake' headlines — harmless to people, ruinous to whoever bought it, and the reason public aquaria keep refusing donated adults. It does not stop growing because the tank is small; it grows deformed instead.
Care
An adult needs 300 x 90 x 90 cm — about 2,550 litres — and never less. Juveniles shoal, adults are solitary, restlessly active, and will chase and nip slower tankmates, so timid or long-finned fish are the wrong company. Despite the vegetarian diet anything small enough to swallow is food. Plants are eaten, heaters get broken, and a panicking 25 kg fish is a genuine risk to thin glass, so use a heavy lid and robust equipment. Buy one only if you already own the pond it will finish its 25 years in.
Diet
Frugivore first: fruit, nuts and seeds, plus insects and small fish opportunistically. Large vegetable-based pellets with apple, banana, courgette, spinach and lettuce; animal protein only occasionally.
Tankmate compatibility
Possible with care (180)
Avoid (238)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
There is no reliable way to sex this species by eye. That is the honest answer, not a gap in our data.
All the methods, with diagramsSimilar species
Same category and the closest water parameters — if this species isn't quite it, start here.
Sold in Lithuania
These Lithuanian shops listed this species in their public catalogue (checked August 8, 2026). Stock moves — ask before you travel.
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Frequently asked questions
- What tank size does a Red-bellied Pacu need?
- A Red-bellied Pacu needs an aquarium of at least 2500 litres (660.4 US gallons) with a footprint at least 300 cm (118.1 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Red-bellied Pacu need?
- Red-bellied Pacu does best at 23–28 °C (73.4–82.4 °F), pH 4.8–7.5 and a general hardness of 0–15 °dGH.
- Is the Red-bellied Pacu suitable for beginners?
- Red-bellied Pacu is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.