Mary Allen
South American predatory fish have no place in home aquariums – with one exception: Red piranhas can be kept satisfactorily, at least by specialists.
There are much different predatory fish in the Amazon region, which arouses aquarists’ passion for collecting. But only very few species can be kept permanently in home aquariums. They are at most suitable for zoo keeping, as they have a high willingness to escape. This means that they react to even the slightest disturbance and shoot uncontrollably through the aquarium, which can lead to injuries.
Nevertheless, young fish of predatory trout tetras (Salminus Maxillofac) are occasionally offered in specialist shops. The nervous fish reach a length of around 60 centimeters and are very skittish. The situation is similar to the wolf tetra (Hydrolycos scomberoides), which also grows to 60 centimeters. Dog tetras (Acestrohynchus sp.), on the other hand, “only” grow to 30 centimeters. But even then they would need aquariums with more than 1000 liters of water.
Red piranhas (Pygocentrus nattereri) are among the frequently kept predatory fish. Five to six specimens can live in aquaria with a volume of 500 liters. There shouldn’t be any hiding places. Planting is also possible.
In trade and sale, young red piranhas are sometimes confused with the similar-looking young of the herbivorous black pacus (Colossoma macropomum). This quickly overwhelms the aquarist, since pacus become true fish giants.
Despite their fearsome teeth, black piranhas are not very aggressive
It has long been known that red piranhas make sounds. Researchers at the University of Liège in Belgium have now taken a closer look at the acoustic repertoire of the fish. They recognized three different sounds. Barking means: Get away from me! – short drumming means: I fight for my food! – and croaking means: Careful, I’m about to bite!
They produce the drumming sound with their drum muscles. These lie above the swim bladder, which also serves as a resonator. The rate of muscle contraction determines the frequencies of the barking and drumming sounds. The softer, croaking sounds are made with the jaws.
The black piranhas (Serrasalmus rhombus) have a large distribution area. As a result, numerous subspecies and local varieties are known, which makes species identification difficult. Little is known about keeping them in aquariums. These fish are usually kept alone.
“When they are young, the diurnal fish hunt in swarms, small groups without hierarchy and only later develop into solitary individuals that stay undercover and lie in wait for prey,” writes the piranha expert Michel Jègu in his book “Serrasalmine”. In the aquarium they would show this behavior very early on – however, they are only fed with dead small fish such as aqua dents (smelt).
In terms of their nature, the black piranhas are classified as less skittish and aggressive than other piranha species. However, based on the size of the teeth alone, they appear more dangerous. With a body length of well over 40 centimeters, the fish are about twice the size of an average red piranha. They are therefore hardly recommended for the home aquarium.