Piranha fish are world famous at this point and a popular culture icon. Their very name conjures images of muddy waters full of small freshwater fish that have razor-sharp teeth and a thirst for blood, like sharks in miniature. The truth is both less and more impressive than this.
While they are very much meat eaters, Piranha care is not at all what you might be thinking! In fact, many of the most common species are downright skittish! Still, you’re better off keeping your fingers outside the tank at all times…Let’s talk more about Piranha care.
In the aquarium, many Piranha fish are quite timid and yet still very dangerous, for reasons we’ll get to soon. The truth is that they do have seriously sharp teeth and true to the legends, they can effortlessly shear flesh from their prey, tankmates…or your hand if they decide to try. Piranha aquarium maintenance is more delicate than is typical for fish tanks but not as scary as you might think.
Piranhas are actually very closely related to Tetras and many live in the same native habitats. They used to be classified in the same family (Characidae) but have since been moved to their own family (Serrasalmidae). Neon, Cardinal, and especially Black Skirt Tetras have more than a few passing resemblances and habits.
Like their tiny cousins, Red-Bellied Piranhas tend to hang in loose shoals rather than true schools. They spend most of their time displaying to one another, giving short chases, and waiting for food to appear.
There are over a dozen genera of piranha in the wild and many species. However, there are only a handful that ever make it into the hobby. And of those, only three are common enough to be readily identifiable by non-Piranha keepers and ichthyologists.
Piranha Species Profiles
There are dozens of Piranha species in the wild but these are the only two you’re likely to ever see. Speciality warehouses and distributors may carry other species on rare occasions. Their care requirements are generally identical to either of these two species, depending on whether they are shoaling/social or solitary/loners.
If you’ve ever stumbled upon a Piranha species at a local pet store or even a museum, chances are you were looking at Red-Bellied Piranhas. 95% of the Piranhas in the trade are this species. Their brilliant red bellies and somewhat social character make them the most appealing Piranhas to care for.
Red Bellies are medium-sized as adults, with 8-10 inches being standard for them. They are also the easiest species to keep with other fish so long as they are kept well fed.
- Scientific Name: Pygocentrus nattereri
- Origin: Amazon Basin, South America
- Length: 8-10 inches
- Aquarium Size: 75+ Gallons
- Temperament: Aggressive; Shy
- Ease of Care: Moderate
Black (White) Piranha
Black Piranhas, also confusingly known as White or Red Eye Piranhas, are the second most common Piranha species. Unlike Red Bellies, they are aggressive, solitary predators that aren’t skittish at all. Since they live alone they don’t group into feeding frenzies.
In fact, they have very cichlid-like confidence that can be intimidating with their razor-sharp teeth. Also, you should know how large they get – up to 20 inches! They will watch you as you move around and may even try to nip at cleaning tools that enter the tank.
One should always keep Black Piranhas alone or with fish too small for it to bother trying to eat, like Guppies and Tetras. They are slow-growing, on the order of an inch per year. But they have a subtle coloration and are incredible show fish, assuming you have the space for one.
- Scientific Names: Serrasalmus rhombeus
- Origin: South America
- Length: 16-20 inches
- Aquarium Size: 180+ gallons
- Temperament: Aggressive
- Ease of Care: Moderate
Are Piranhas Legal to Keep?
Here’s something you may not know: Piranhas aren’t legal in many US states. They require warm, tropical temperatures to survive and would not be able to live year-round in all but the warmest climates.
A Piranha population can’t survive in most of the country. But they’ve captured the popular imagination enough that a significant number of states have banned them despite there being no danger of wild Piranhas naturalizing.
Many times a “Piranha” found in local waters is actually a Pacu, as this article by the Guardian found.
Piranha Fish Care
So long as you’re aware of the challenges involved, caring for Piranhas is fairly straightforward.
Piranha Fish Tank Size
A spacious aquarium is paramount for Piranhas for several reasons. One reason is that their sharp teeth make them very messy eaters that require a carnivorous diet. Meat-eating fish that chew their food release tons of flesh particles into the water that decay and contribute to ammonia and nitrates. A mature, well-cycled aquarium with a powerful canister filter is mandatory for their health.
Aquarium size is even more important for the Black Piranha, which reaches 20 inches as an adult. Fortunately, they are extremely slow-growing fish. They may only grow one inch per year, so you have at least a decade before you’ll need to go beyond 100 gallons.
Red-Bellied Piranhas, on the other hand, can be found as youngsters as small as an inch long! They do grow quickly but can live comfortably as adults in tanks as small as 75 gallons. Just remember that they are shoaling fish and should be kept in groups of 3-12 whenever possible.
Another important reason Piranhas require space is because they are extremely skittish fish! Far from the ultimate Amazonian predators (except for the Black Piranha), Red-Bellied Piranhas are very easily frightened by sudden movements because many things, including people, love eating them.
- The ISTA in-line external heater is designed for...
- The ISTA External Heater must be used in a...
- The ISTA External Heater is easily installed by...
In fact, you should avoid using standard glass heaters in a Piranha tank as they are likely to dash against it, shattering it and potentially electrocuting your fish. Expert Piranha keepers use either heater guards or in-line heaters to avoid fatal damage.
Water Conditions for Piranha Fish
As I mentioned earlier, Piranhas are messy carnivores. So heavy filtration and frequent water changes are essential to keeping their water free of ammonia and other nitrogenous waste products.
For parameters, you’re looking at standard tropical South American conditions, which range from a pH of 5.5-7.0 and temperatures from 75-85℉. Piranhas require extremely warm waters as they are found in the shallow, slow-flowing portions of rivers and streams.
Piranhas inhabit waters in South America that are stained a dark tea color by plant tannins and humic acids. These chemicals can drop the pH very low. While they don’t require a blackwater aquarium they do need a pH that’s on the moderate to low side to stay healthy.
You may already be thinking about how to perform water changes in a Piranha tank. Some aquarists decide they aren’t intimidated by their fish and simply go in and wash the glass and vacuum the gravel normally. While they are unlikely to be bitten, it’s also not out of the realm of possibility.
The problem with Red Belly Piranhas isn’t that they are aggressive, it’s that they are unpredictable. When feeling threatened, they both flee and bite. So if your arm is in their way, and they are seriously fast fish, they may snap at it in self-defense. It’s better to attach your siphon hose to a pole or use a siphon long enough to not require you sticking your hands into the tank.
Black Piranhas are much bolder, making cleaning a real challenge. They will even bite at magnetic glass cleaners and are often waiting at the surface to feed when you open the lid for water changes…
Plants and Decorations
Plants are an important part of Piranha care. They are very plant safe for such large fish. In fact, plants are highly recommended for Red-Bellied Piranhas because they provide nearby cover, helping them feel less exposed and thus, skittish.
Since they are fairly large, active fish, they may bowl over thickly planted or loosely rooted plants. And their love of extremely warm temperatures may be too much for many plants, which prefer being kept below 80℉. Any of the plants recommended for Discus and Angelfish are great choices for Piranha aquariums as they thrive in hot, acidic conditions.
You need to be very intentional with choosing your decorations because Piranhas will crash into them when startled. Sharp edged rocks and pointed driftwood should be avoided in favor of smooth edged pieces.
- Establishes similar water conditions to those...
- Help simulate the onset of the rainy season for...
- Enhances the effectiveness of plant nutrient...
Driftwood also provides a slow-release source of plant tannins, which buffer the pH towards acidity. If you’re looking to provide true blackwater conditions for your aquarium fish, consider also using a blackwater extract formula. This way, water changes won’t remove what few tannins your driftwood leeches over time.
Tank Mates for Piranha Fish
Choosing tank mates for Piranhas is one of the more challenging aspects of keeping them. Unfortunately, your best bets are either other Piranhas or freshwater fish that you don’t mind losing if your Piranhas decide they look tasty.
Well-fed Red Belly Piranhas are fairly tame towards their tank mates and can be kept alongside other fish their size or larger. Large Cichlids like Peacock Bass, armored Catfish, and related fish from South America like Pacus and Silver Dollars are your safest choices. However, you can also try keeping them with tiny fish that are beneath their notice. Guppies, Zebra Danios, and other fish species are often too small to be worth chasing if your Piranhas are fed often. No guarantees, though.
Good Tank Mates for Red Belly Piranhas:
- Other Red Belly Piranhas
- Peaceful to Semi-Aggressive Community Fish (Cichlids, many Catfish, large Barbs, etc)
- Guppies, Danios, and other small Community Fish
- Armored Catfish
Poor Tank Mates for Red Belly Piranhas:
- Gouramis, Platies, Mollies, Rainbowfish, Angelfish, and other medium-sized Community Fish
- Territorial, Aggressive fish (Certain Cichlids, Catfish, etc)
Black Piranhas must be kept solitary or again, with aquarium fish that are beneath their notice. They are likely going to take a chunk out of any sizable tank mate that’s around if you miss a feeding. Or they may bite just because they felt like it.
Feeding Piranha Fish
Feeding Piranha fish, on the other hand, is just about the easiest aspect of keeping them! As you might expect, Piranhas eat any sort of live or dead meat you offer them. But that doesn’t mean that you really should give them anything.
While it’s okay to offer it to them occasionally, birds and mammals aren’t too good for them. Their meat is much fattier than aquatic animals, which can lead to fat building up in their body cavity and especially the liver. Piranhas evolved to eat mostly aquatic fare with the occasional fruit and nuts dropped from overhanging trees.
Chunks of thawed shellfish and white fish are the best thing you can feed them. Frozen mussels, squid, shrimp, and any cheap white fish from the seafood aisle will do. Feeder fish are a poor choice because they are starved, nutritionally speaking. They are fed poor-quality flakes for their short lives and are loaded with bacteria and parasites that get passed right onto the Piranha.
They also don’t need to be fed every day. One hearty feeding every other day is enough for Piranhas. They will eat heavily during a single feeding and then digest for a day.
Breeding Piranha Fish
Breeding is one aspect of Piranha care that you may be fortunate to witness if you manage to succeed at everything discussed here! They spawn occasionally but not very often in home aquariums. It takes the right temperatures, age, pairs, and water conditions to pull it off.
Red Belly Piranhas aren’t sexually dimorphic – meaning, you can’t tell them apart by looking. The fish somehow know; likely through behavioral and hormonal cues. Females will swell slightly when gravid and preparing to spawn.
Captive spawnings almost always take place when groups of 6 or more fish are kept together in tanks larger than 150 gallons. They pair off and the male will dig a shallow pit; a soft substrate like sand makes his job much easier. The female deposits her eggs, the male fertilizes them, and then drives her and any other fish that approaches off until they hatch.
The eggs take around 4 days to develop and hatch. Once the fry emerge, they subsist solely on their yolk sacs for another 4 days, though. Once they run out of yolk they are free-swimming and able to feed on brine shrimp nauplii, micro worms, and other small, live prey.
You should siphon them from the male’s nest into a fry rearing tank at this point or sooner since he will stop caring for them and the fry will be eaten by other fish or sucked into the filter. Red-Bellied Piranhas grow quite rapidly, around ½ – 1 inch per month, and are ready for resale to local aquarists and pet stores in just a few weeks!
Most of these care tips apply to both the Red Bellied Piranha because it is by far the most common species of Piranha fish in the hobby. However, if you want to try keeping a Black Piranha, you are still going to be well informed by this care guide.
Just remember that the Red Bellied Piranha is a skittish fish that needs special care and a meaty diet. And try not to reach into the tank too often and few mishaps should occur.
More Frequently Asked Questions about Piranha Fish
Still not sure if Piranha fish are right for you? Then let’s talk about a few more facts surrounding piranha fish and piranha fish care.
Can Piranha Fish Eat Humans?
Yes, they can. Piranha fish have powerful jaws and large, razor-sharp teeth that they use to slice chunks of flesh from other animals. They don’t usually eat animals larger than them but if hungry or frightened they can quickly dash in and bite. This behavior can then trigger other Red-Bellied Piranha fish to follow, causing feeding frenzies to erupt.
Is Piranha Fish Aggressive?
Red-Bellied Piranha fish and other Piranha species are usually not very aggressive. But Black Piranhas are very aggressive and will kill most other fish in the same aquarium as them.
Can You Keep Piranha Fish as Pets?
Piranha fish belong to the family Serrasalmidae, which includes many popular aquarium fish from South American rivers, like Pacus and Silver Dollars. They can be kept as pets but they are moderate to difficult to care for. Red-Bellied Piranha fish are very skittish and unpredictable, which makes them sometimes dangerous. But when well fed and kept in stable conditions they calm down enough to make beautiful and long-lived pets. Black Piranhas are much calmer but have to be kept alone because they are large and very territorial.
How Fast Can a Piranha Eat a Human?
Experts from Popular Science found that between 300 and 500 Piranha fish would decapitate a human in around 5 minutes. In Piranha-infested waters, the fish will enter a feeding frenzy where they quickly strip a body bare of flesh within mere minutes. And since they swim in schools it’s entirely possible for them to completely eat a person.
In South America, this is most dangerous in the dry season when the water levels are very low. The piranha fish have likely eaten everything else in a body of water and are starving. A person suddenly jumping into those waters may then be attacked by a school of Red-Bellied Piranha.