Piranha
South American predatory fish famous for their sharp teeth. In the aquarium they are often shy and fearful. They require large aquariums.
Detailed explanation
Pygocentrus nattereri (Red Belly Piranha) are the most common in aquariums. They grow up to 25-30 cm and live in herds of at least 5-6 individuals.
Contrary to legend they are often shy and fearful. They hide behind decorations at the slightest sudden movement.
They require large aquariums (400+ litres for a group), soft, acidic water (pH 6.0-7.0), temperature 24-28 degrees. Powerful filtration for high organic load.
The diet is carnivorous: raw fish, shrimp, earthworms. Do not feed with red mammalian meat (too fatty). In many countries detention is regulated.