Beauty or Beast

Piranhas are shoaling fish that belong to the family Serrasalmidae. They are related to pacu, silver dollars and tetras. There is some debate as to how many different species there are, but it is thought to be somewhere between 20 and 50. The most common piranha in the aquarium trade is the red bellied, Pygocentrus nattereri, a silver-grey fish with bright red-orange in the throat, breast and stomach area. Females tend to be larger and less colorful. Several other species are available from time to time, including the black piranha, Serrasalmus rhombeus and wimpel piranha, Catoprion mento, which is not actually a true piranha but rather a close relative. Most species are not as aggressive as their reputation suggests and many are omnivores, which include plants, seeds and fruit in their diet. Properly kept, they are interesting and beautiful fish, but they have a few special needs, and caring for them long term requires true commitment. Piranhas are banned as pets in many areas, particularly in the southern United States, so check local regulations before purchasing them, especially online. 

A Piranha's Natural Habitat

Piranhas are found in the Amazon Basin, Rio Paraguay, Rio Paraná and several other river systems of South America. They inhabit open water channels, small tributaries, shallow backwaters, oxbows and temporary forest pools created during the rainy season. 

Water Requirements for Piranhas

While piranhas are found in soft, low pH water in the wild, virtually all red-bellies sold today are raised commercially in water that often has a higher pH and alkalinity than their native habitats. Most other species are wild-caught but can be acclimated to tap water as long as extremes are avoided. pH should be between 6.5 and 7.8, alkalinity between 3° and 8° (50 ppm to 140 ppm), and temperature between 75° and 80° F. If the aquarium is kept in a room below 75°, use an Aqueon Aquarium Heater to maintain proper temperature. Like many tetras and silver scaled fish, piranhas are sensitive to sudden temperature changes and are prone to ick if the temperature is too low. They are also sensitive to certain medications, so read directions carefully before treating them. Maintain good filtration and change 10% of the water weekly or 25% every 2 weeks using an Aqueon Aquarium Water Changer or Siphon Vacuum Gravel Cleaner. Do not forget to treat tap water with Aqueon Water Conditioner before refilling your aquarium! 

Housing Requirements for Piranhas

Baby piranhas can be kept temporarily in aquariums as small as 20 gallons, but in the long run, adults will need at least 100 gallons or more depending on how many you have. They will be less stressed and show their best colors in a well-decorated aquarium with a dark substrate and subdued lighting. Keep a secure lid on the aquarium to prevent them from jumping out if they feel scared or threatened. Provide mild but steady current. A slightly oversized filter with good mechanical and biological capabilities or the use of multiple filters is recommended as adults are messy eaters and maintaining good water quality can be a challenge. Careful consideration should be given before buying piranhas as they get big, eat a lot, make a mess and live a long time. Returning them to the fish store or re-homing them, while certainly an option in dire circumstances, should never be a decision that is made lightly. 

Behavior/Compatibility for Piranhas

Young piranhas school for safety from larger predators, but as they grow to adulthood they tend to hang out in loose groups. Some experts recommend keeping them individually or in groups of 5 or more to avoid cannibalism. They can be shy and a bit skittish, especially when kept singly or when they are first introduced into an aquarium. They often hide in the corner when the tank is being cleaned, but it is best to always know where they are when working in the aquarium, especially if you have more than one. Piranhas do not attack as a rule, so there is little to fear by putting your hand in the aquarium. However, avoid provoking or cornering them, as this will almost always elicit a defensive response. If possible, buy babies so they get used to hands and cleaning equipment in the tank before they grow larger. When netted, palm-sized and larger piranhas typically destroy the net by biting holes in it, and even 3" fish are capable of chomping right through a fish bag, so these individuals are best transported in a bucket. As far as tank mates are concerned, while they are known to tolerate plecostomus and other large predatory fish on occasion, piranhas should be kept by themselves. 

What Do Piranhas Eat?

Piranhas in the wild are generalists, feeding on fish, crustaceans, insects, plants, fruits, nuts and seeds. Do not feed your piranhas live goldfish or other feeder fish if you can help it! They can transfer diseases and are not nutritionally balanced. Avoid buying adult piranhas that will only eat live feeder fish. Also, avoid feeding piranhas chicken, beef heart or other mammalian foods, as they may contain fats your fish cannot metabolize that can cause health problems over time. Young piranhas will thrive on Aqueon® Tropical Flakes, Color Flakes, Tropical Granules, Shrimp Pellets and Cichlid Pellets along with frozen tropical fish foods. Adults can be fed medium to jumbo Aqueon® Cichlid Pellets and Monster Fish Medley, as well as frozen krill and other large frozen aquarium fish foods. For best results, rotate their diet regularly and feed only what they can consume in 2 to 3 minutes. Net or siphon out uneaten food immediately. When keeping more than one piranha, make sure they do not go hungry or they may go after each other. 

Piranhas Breeding Level – Intermediate

It is not uncommon for piranhas to breed in captivity. Some breeders report success after a large water change. Best results are achieved with groups of 6 or more, although a single male/female pair will readily spawn if conditions are right. Eggs are laid in a pit and hatch after 3 to 5 days, depending on temperature.