Piranha

Characteristics, Origin, and Helpful Information for Hobbyists

Red Belly Piranha taken by Dr Thomas R, Reich In Vancouver Canada
Thomas R. Reich PhD

When you think piranha, do you think voracious, man-eating mean little fish with rows of sharp, vicious teeth capable of picking clean the skeleton of a human? On the contrary, 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 feast on other fish or wounded animals—not humans.

More humans bite into piranhas as a food source than the other way around. 

There are more than 30 varieties of piranha, and they span the spectrum from vicious gang killers to peaceful scavengers. In most cases, they are no more violent than angelfish. Before you get one make sure to check your local and state laws regarding piranha. In about half of the U.S. states, owning piranha is banned or tightly regulated. Because of their aggression and difficulty maintaining them, these fish are not recommended for hobbyists.

Characteristics

Scientific NameSerrasalmus nattereri 
SynonymsSerrasalmus spilopleura, S. gibbus, S. rhombeus, S. maculatus, Pygocentrus nattereri, Rooseveltiella nattereri
Common NamesBlack shoulder piranha, red bellied piranha, blacktail piranha, black piranha
FamilySerrasalmidae
Origin10 inches
SocialAggressive
Lifespan10 years
Tank LevelAll
Minimum Tank Size40 gallons per fish
DietOmnivore
BreedingEgglayer
CareAdvanced
pH6.0 to 7.5
Hardness4 to 18 dGH
Temperature74 to 82 F (23 to 28 C)

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 water systems.

They inhabit all sizes of running water like rivers, tributaries, and creeks. Also, they are 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 varieties of piranha, but perhaps the most popular species in the aquarium trade is the red-bellied piranha. These fish have powerful bodies that are high, thick, and laterally compressed. Like all piranhas, they have a keel-like edge that runs along the upper body from head to dorsal fin and along the belly on the lower body. They are all 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 amazing adult colors. Body colors can be variable, but mostly the back is a steel gray and the rest of the body is a silvery gold with a bright orangish-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 more 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.

These fish are not considered a good fish for a community aquarium. Frequently, piranhas can be kept with small, peaceful fish such as neon tetras and guppies, provided that the piranha is large enough and has been kept on a high-quality diet so as not to consider these fish as food. 

Piranha Habitat and Care

Piranhas are big, 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 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. These fish will be less skittish and shy in an aquarium with a lot of hiding places. However, they also 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

All species of piranha require a high protein diet, taking meat, liver, fish, or any other flesh, which will satisfy their insatiable need and constant hunger.  They cannot eat and 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, 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 really desirable as it puts a huge pollution load on the aquarium. This omnivorous species has been reported to eat some aquarium plants.  

Sexual Differences

Piranhas do not have many visual differences between the sexes.

Around the mating time,  a female may get fuller in the belly as she fills with eggs, and males may get more colorful before spawning.

Breeding the Piranha

Unlike other characins, it turns out that piranha are uncharacteristically parental. In nature, many species use water plants as hatcheries. In the wild, piranha breed when the rainy season sets in about 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 then become free-swimming. The 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 breeds in aquariums, Serrasalmus spiopleura is one of the few species which has actually done so with success. The female deposits her eggs carefully on aquatic plants, which is unlike the usual erratic spawning behavior of most characins. 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, and this may mean you. 

More Pet Fish Breeds and Further Research

Check out other freshwater fish that might be a nice addition to your tank.

If you would to learn about maintaining saltwater fish or other kinds of freshwater fish, check out all of the other pet fish breed profiles.