Piranha Fish Species Profile

Pirahnas are not actually like the fish depicted in Holywood movies. A piranha averages only 10 inches in size, and it is a cousin of the neon tetra. It is true that a hungry piranha will bite almost anything, even other piranhas, however, piranha normally bite on other fish or wounded animals—not humans. Many more humans bite into piranhas as a food source than the other way around. 

There are more than 30 varieties of piranha, and they run the spectrum from gang mobsters to peaceful scavengers. In most cases though, they are no more aggressive than angelfish. Before you get one make sure to check your local and state laws regarding piranha. In most of the states in the US, owning piranha is banned or tightly regulated in order to protect wild ecosystems. Because of their aggression and the difficulty in maintaining them, these fish are not recommended for hobbyists.

Characteristics

Origin and Distribution

Piranha are found across a wide geographical range in South America, including Venezuela, Brazil, Peru, Guyana, Bolivia, Paraguay, Argentina, Colombia, Ecuador, and Uruguay. They live in the Amazon River basin as well as in the basins of the Paraguay, Parana, and Essequibo rivers. They also inhabit the coastal rivers of northeastern Brazil and numerous other small waterways.

Piranha mainly inhabit rivers, tributaries, and creeks. They are also found in larger bodies of water including lakes, pools, flooded forests, and the Pantanal wetlands of southwestern Brazil. These schooling piranha are generally found in groups of 20 to 30 fish.

Colors and Markings

There are many species of piranha, but the most popular species in the aquarium trade is the red-bellied piranha. These fish have powerful bodies that are tall and laterally compressed, but they are thick-bodied. They are recognizable by the convex shape of their head and massive, bulldog-like lower jaw. With a large, powerful tail and a streamlined body covered with tiny scales, they are very fast and agile swimmers. They also have a small adipose fin between the tail and dorsal fin, a characteristic of all characins.

The red belly piranha has bright adult coloring. Body color can vary, but in most the back is a steel gray and the rest of the body is a silvery gold with a bright orange-red or red colored throat, belly, and anal fin. It has large black spots on the sides, though they often fade with age, and it sparkles with many shiny scales. In its juvenile form, it is silver colored with dark spots. Some individuals have such intense gold-speckling that they are sometimes called gold-dust piranha.

Tankmates

Piranha have odd companionship requirements. As juveniles, piranhas are schooling fish and should be kept in groups. However, as they mature, many varieties of piranhas become more solitary and may attack others of the same species.

A school of piranha is incredibly hierarchal and there will be a clear chain of command. Generally, the largest and most aggressive fish will become dominant. This fish will claim the best spots in the tank and be the first to feed. A challenge by another fish will result in aggressive behavior such as chasing, occasionally taking a bite out of fin, and even inflicting wounds.

Piranha Habitat and Care

Piranhas are messy feeders, so they need ample filtration and regular water changes to handle the bioload. You will need to change 30 to 50 percent of the tank water every other week.

A single specimen requires an aquarium of at least 40 gallons, but a group will require a much bigger tank. These apprehensive fish will be less timid if kept in a school of four or more and will be less skittish and shy in an aquarium with many hiding places. However, they do need plenty of swimming space.

Add bogwood and place plants around the perimeter to offer some cover; this helps them feel at home while leaving an open area for swimming. Provide a substrate of sand or fine gravel, and use dim lighting.

Piranha Diet and Feeding

All species of piranha require a high protein diet, taking meat, liver, fish, or any other flesh. They will not accept flake or pellet food. They will seize and devour any fish of any size introduced to their tank, gulping small fish whole, and slashing out large pieces from larger fish, not even hesitating to attack and eat fish three times their size as soon as they are introduced to a tank they are in. 

In captivity, piranha they can be trained to eat whole dead fish, such as frozen silversides and lancefish, as well as a variety of other meaty foods such as prawn, mussels, and fish flesh. They will eat live foods such as feeder fish, earthworms, and river shrimp, but this is not desirable as it puts a huge pollution load on the aquarium. This omnivorous species has been reported to eat some aquarium plants as well.  

Gender Differences

Piranhas do not have any distinguishable visual differences between the sexes. Around mating time, a female may get fuller in the belly as she fills with eggs, and males may get more brightly colored before spawning.

Breeding the Piranha

Unlike other characins, the piranha species are uncharacteristically parental. In nature, many use plants as hatcheries. In the wild, piranha breed when the rainy season sets in during January or February, but they seem to breed whenever conditions are right and water plants are plentiful. The female deposits her eggs on water plants or roots, which are then fertilized by the male.

Upon hatching, the fry stay attached to the vegetation in clusters until they have absorbed most of the yolk sac and become free-swimming. The parental male will attack anything coming close to the fry during this state, which is why, some scientists theorize, people get bitten.

Although you will rarely find piranha that breed in aquariums, Serrasalmus spiopleura is one of the few species which has actually done so with success. The male guards the eggs and the fry. Parents usually ignore the fry; they do not chase or eat them. The fry has been observed swimming around the adults. If you do breed piranha, beware! Since piranha viciously guard their eggs, they may bite the hand that feeds them!

More Pet Fish Species and Further Research

If you are interested in similar species, here are other fish in the characin family; many should also be avoided in the community tank hobby:

• Characin Genus Information
• Silver Dollar Species Profile

Check out additional fish species profiles for more information on other freshwater fish.