As a group of fish, Pacu are probably not a good choice of most aquaria. Initially they might look small enough to be a featured fish, but the relative small nature of the juvenile quickly disappears with maturity. Assuming though that a Pacu or several Pacu have been obtained then there are some things that should be known when it comes to caring for them.
Pacu are far from being the most difficult of fish to care for in an aquarium. Caring for them though starts by ensuring that they are housed in the correct sized aquarium tank. A Pacu could easily grow to 80cm if looked after correctly, and so any tank will need to be a minimum of 250cm in size, and ideally have a capacity of more than 700 litres. It is of course better to house other fish with the Pacu, who are in their way quite sociable. Other suitable fish are those of a similar size, including cichlids and Oscar fish, anything smaller may well become a meal for the Pacu.
The water in the tank should be between 25 and 28 degrees Centigrade, with a roughly neutral pH level.
As mentioned before the Pacu are sociable, but as juveniles they can be on the shy side and will benefit from caves and other hiding places. Many other forms of decoration, things which are often found with smaller aquaria fish, are though surplus to requirement as they will often end up being eaten by the Pacu.
An important part of caring for Pacu is of course their diet. Pacu will eat almost anything and are strictly speaking omnivores. They do though have a preference for a more plant and algae based diet. This is often supplemented with vegetables and fruit.
The Pacu have a large level of food intake, as befits a large fish, but this of course leads to a large amount of waste, including food waste. To properly care for the Pacu therefore it is essential that there is a good filtering system in place, and a good water replenishment process. The Pacu will need clean water in which to live, or else their lifespan will diminish from a possible 25 years, down to less than 5 years.
Given the right sized aquarium with clean water, and the proper diet, Pacu are one of the easiest of aquaria fish to look after, and can in their way build up a bond with their owner. The Pacu though are not a fish that should in any way be recommended to the majority of aquarium owners, who will find that the fish will be too large for them to care for properly.