Tambaqui (Black Pacu)

Origin and Ecological Role:

Native to the Amazon, this giant plays a crucial ecological role. During the flooded forest season, it swims among the trees swallowing the seeds of fallen fruits. The seeds, resisting digestion, are scattered tens of kilometers away (zoochory), making the Tambaqui the main silent forester of the Amazon.

Morphology:

As a juvenile it is silvery with a reddish belly, often mistaken for Red-bellied Piranhas (but the Piranha has a prominent, protruding lower jaw, the Pacu has equal jaws). As it grows, the Pacu becomes an imposing and thick pitch-black-grey monolith with visible scales.

Setup (Dimensional Danger):

The Tambaqui is a victim of the trade. Sold as a "Vegetarian Piranha" for a few dollars when it is the size of a coin, it condemns the aquarist to a disaster. This animal is a "Tank Buster". Its power is such that if a 15 kg adult gets scared and crashes against the glass or the heater (causing the hot glass to explode in the water), the damage is catastrophic. No standard home aquarium (not even a 600-liter / 150-gallon one) can house it. The tanks, huge and bare-bottom, must have very thick glass, no unstable rocks or sharp wood.

Filtration:

Eating whole fruits and vegetables involves the evacuation of mastodontic polluting masses. Without a trickle filter suitable for ponds and large indoor pools, the tank will collapse under ammonia.

Diet (The Herbivore with Molars):

Open the mouth of an adult Pacu and you will find two rows of teeth that look disturbingly like human teeth. They are used to crush *seringueira* (rubber tree nuts). In captivity, feed this black hole with whole blanched sweet potatoes, peas, lots of blanched lettuce, and cheap koi pond pellets. If you keep your fingers in the water with food nearby, their eagerness can accidentally crush your phalanges.