The pacu is a tropical fish from the Serrasalminae family (serrated salmon family) which is an extension of the characids often referred to as tetras. They are characins that closely resemble the piranhas. The only difference is in the teeth structure which is sharp and pointed in case of piranhas and square-sharped in case of pacu fish. Also unlike piranhas, pacu are peaceful and don't have an aggressive temperament. Appearance and Variety These fish have large eyes and a tall and laterally compressed body with an arched back. A normal adult grows between 12 - 24 inches, though few grow as large as 30 inches and weigh as heavy as 50 lbs. However their size gets inhibited if they are bred in aquariums. The lifespan is between 5 - 15 years or even more. The diet mainly consists of flakes, pellets, and frozen foods like vegetables if they are bred in aquariums or huge tanks. In the wild, they feed on snails, insects, small fish, and decaying vegetation. The most famous variety are the red belly pacu and the black pacu, which is better known by its local name tambaqui. It is sometimes nicknamed as the red belly piranha in fisheries. Pacu fish are easy to breed because of their tolerance to low levels of oxygen. Also they do not require any specific protein diets. Black pacu fish are raised in freshwater aquaculture farms because they have strong immunity against diseases and are also consumed by humans widely. They are found predominantly in the flood plains. They have a powerful sense of smell and vision when it comes to food. Their appetite increases during floods and they sustain by feeding on hard nuts and rubber tree seeds. They are also considered as one of the best tropical delicacies specially when barbecued. After being discovered in the USA, they have been branded as one of the exotic species. They find a laudable position even in Theodore Roosevelt's book Through the Brazilian Wilderness as savory delicacies. Care Tips Caring for this species becomes a herculean task when it comes to breeding them in aquariums. This is because of their huge size and prey hunting instincts. However, commercially, they are a big success and are bred in massive tanks. To breed pacu, the tanks must have a capacity to hold minimum 50 gallons of water for juveniles and at least 200 gallons of water for adults. The tank water must be filtered regularly and the temperature should be maintained between 23 - 28ºC. Also the pH balance of water must be maintained between 6.5 - 7 and the hardness up to 20 dH. It is recommended that the tanks have enough hiding places as these fish have prey hunting habits. Juveniles enjoy the company of other fish, but as they mature, they tend to become solitary by nature. However, generally, they have a mild temperament and get along well with other species like the Oscar and Clown Knife fish. At times, it can also be bred in indoor ponds. Any living creature responds to companionship and love. Pacu are believed to respond well to good care and good food. They are beautiful fish that serve recreational, commercial, and culinary purposes of humans.