If you are looking to provide a home to greatly extravagant creatures such as piranhas, you are probably already aware of the fact that these unique fish do require a certain amount of extra planning and care.

They are surrounded by a mysterious feeling and are often showcased as overly aggressive and dangerous-to-humans, but they are actually not such vindictive killing machines as the media tend to present them.

But they do grow to a fairly large size and they are omnivorous, meaning that they certainly require massive tanks during their life in captivity. Therefore, here comes our complete guide on the ideal piranha tank size.

As a starting point, many owners like to keep their juvenile piranhas in 50- or 60-gallon tanks, which is totally fine. However, they do tend to grow quite quickly, so I would recommend getting a 75-gallon solution which would suit them much better.

Size of a Piranha

Once your juvenile piranhas fully develop and reach their adulthood size, they will become quite the massive, noteworthy creatures. And this is something that you should definitely keep in mind.

There are several popularly available choices of different piranhas species in the aquarist hobby, and the size varies slightly depending on the one you choose to house.

The red-bellied piranha, which is one of the most desired options among aquarium keepers nowadays, can grow up to even a foot (or 30 centimeters) during their adult phase. But piranhas are not just large creatures.

They are also extremely strong and feature resistant body shapes, so they can weigh a lot, too. If we take again the example of a red-bellied piranha, you can expect it to reach a weight of 4 pounds (or 1,8 kilograms).

These distinctive fish require lots of space to thrive. They are large and active living beings that produce fairly amounts of waste, so tank size is crucial and should present the basic predisposition for any person who decides to have them around their home.

Minimum Tank Size for Piranha

The very minimum size to house 4 red-bellied piranhas (juveniles!) is 75-gallons. This is also the very minimum number of piranha specimens to keep. Indeed, they are schooling fish, meaning that they can thrive only when there is a functional group of at least 4 specimens. 

While they are young, you may feel free to add some suitable tank mates to such an aquarium, too. A good option are other schooling fish but much smaller in size, such as neon tetras. 

That said, we have to point out that this can only work as a temporary home for young fish, which have still not reached their full body size. Apart from such cases, we highly discourage housing these definitive fish into such small-sized tanks.

Best Tank Size for Piranha

As a definite, long-term aquatic home for your piranha pets, size is vital. If you plan of keeping around 6 adult specimens and perhaps even some tiny schooling fish in there, we suggest to setup nothing less than a 125-gallon tank.

This will ensure that all of your fish have enough space to thrive, but also to keep their water parameters stable at all times. And, as further advice – the bigger your tank is, the easier it will be, both for yourself and your fish.

Cramped spaces can quickly develop into a nightmare for their keepers. From high territorialism and aggressive behavior among fish, to spikes in ammonia levels to life-threatening danger to your beloved pets literally dying out. Therefore, prevention is always the best medicine.

How Many Piranhas Should You Keep Together?

Piranhas are massive schooling fish that require lots of space. The general thumb rule of providing 1 gallon of water per 1 inch of fish which is substantially applied among modern aquariums is absolutely not to be used here.

Piranhas are exclusive creatures and require therefore exclusive rules to be set. Accordingly, plan of ensuring at least 20 gallons of water per 1 adult specimen, and never less than 75 gallons as a starting tank, as you will otherwise have huge difficulties in maintaining stable water parameters.

Piranhas are schooling fish and require consequentially to be housed in schools. In order for them to create a well-functioning group, you should adopt at least 4 specimens. Or, even better, 6.

Can You Keep Piranhas in a 55-Gallon Tank?

In theory, you could keep 3 red-bellied piranhas inside a 55-gallon tank. However, this is far from ideal. As already mentioned earlier, the very minimum size for a school of piranhas is 75 gallons, as this is the starting point to provide them with stable water parameters.

If these are not maintained, you are risking for your fish pets becoming overly stressed, aggressive, and prone to diseases and infections.

As an alternative, you may choose to house a solitary species inside a 55-gallon tank- the black piranha.

This majestic creature prefers staying alone during its life in captivity, and it should have plenty of space inside a 55-gallon home. And you should have no issue in obtaining stable water specifications.

Wrapping Up

Setting up a home for such mysterious and outstanding aquatic creatures is certainly something that every keeper wants to get right from the very beginning. And the best point to start with is choosing an appropriately sized tank.

With most piranha species being massive-sized schooling fish, you should house at least 4 or 6 of them in order to ensure the basic predispositions for them to thrive.

Plus, they require at least 20 gallons of water per specimen, but large tanks are also much easier to keep stable, as there will obviously be quite a lot of waste released by such huge omnivores.

Adding to that, these extravagant fish are active swimmers, so you can provide plenty of resistant plants around their tank, but make sure to leave lots of open space for their swimming activities, too.

If you get the right tank size and manage to setup it correctly, you are facing years and years of a shared life with these unique companions.

Written by Fabian

Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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