Many of the freshwater fish species, such as the red scat, originate from the tropical Pacific areas. Others, like the Boesemann rainbow-fish, the perch, the fat chub, the silver crucian, the marble crucian, the mullet, the nose-carp and the eel are known in Europe, too. The white amur originally inhabited the large rivers of China and the middle and lower stretches of the Amur. It was first stocked in Hungary in 1963. It is a herbivorous species that can reach a large size, weighing as much as 30-40 kg.

Tambaqui or black pacu
Location, habitats: the Amazon River and its drainage area, South America. Food: fruits, herbivorous. Pacus are related to piranhas, they are similarly built animals, the most apparent difference being that their eyes are much larger, compared to their bodies, and pacus always grow larger. A fully grown piranha is not larger than 30cm, while an adult pacu can exceed 80cm. The pacu also has teeth in its mouth but they are not sharp and serve to crumble the food. Its head is smaller than its predator relative's.

The red piranha or Roosevelt salmon lives in the Amazon River and its drainage area, in South America. Food: predator. These bloodthirsty predators form groups of hundreds or even a thousand fish and have earned a terrifying reputation: they do not hesitate to attack the largest preys and oxen, horses or even humans can fall victim of the sharp teeth. They can be attracted by the smallest splash or noise and the smell of blood simply drives them wild. The young animals are silvery, while the grown fish are greyish with orange stripes on the sides. Their colour becomes more vivid during spawning-time. As they are very voracious, they grow fast and the fully grown fish are 25-30 cm long. The natives consider them valuable for their tasty flesh. They have successfully spawned in the Tropicarium several times and we have managed to grow thousands of young fish in the quarantine.

Another interesting fish is the Arowana or Asian bonytongue, which inhabits the Amazon River and its drainage area. Food: insects and fish. The species belongs to the family of bonytongues and it can be considered the remaining representative of an ancient group that was once spread all over the world. The fish have a characteristic shape with an almost vertical mouth opening and the two feelers on the lower jaw. There are large bones around their eyes. Their tongue is largely ossified, hence the name. They are able to breathe in the air from the atmosphere. They are greedy predators, willing to attack smaller fish of their own species and they mainly stay in the upper region of the water. They can jump as high as 1 meter from the water. It is a fast-growing species: the fish can grow as long as 25-30 cm at the age of six months and reach a maximum length of 45 cm. They become mature at the age of 3-4 years and they take care of their offspring in an unusual way as they are mouth-breeders like some tropical bass species.