Piranha Compatibility
Questions pop up often about what tankmates could possibly be kept with piranhas. The final say is this: Nothing can be SAFELY kept with piranhas!
You constantly run the wisk of all tankmates being eaten if housed with piranhas and it is highly reccommended that all piranhas regardless of species only be kept in a species-specific tank. Shoaling species such as Pygocentrus nattereri must be kept in shoals, but everything other else is far better suited to live as the sole individual in the tank.
There are some risky, yet possible situations...
Shoaling Pygocentrus:
Before I start, let it be known that different Pygocentrus species will not actually shoal together; they will only tolerate each other. (I.E.: you cant put one P.attereri, one P. piraya, and one P. cariba together and expect them to shoal with each other, you need 3-4 specimes of each species for shoaling. If you keep 3 different species singly, they will just avoid each other).
It is possible to house different Pygocentrus species together in the same tank such as Pygocentrus cariba, Pygocentrus nattereri, and Pygocentrus piraya. This is risky, but considered "easy" if the proper precautions are taken.
1. A tank large enough to house a shoal of all species. Heres a guideline: Take the minimum reccomended tank size for shoal species A, take the minimum tank size for tak size for shoal species B, and if applicable the minimum tank size for species c,d, and so on. Add all of the minimum tank size together, then add AT LEAST 25% of that volume to the tank and you have a minimum tank size for housing different Pygocentrus species together. For example, the minimum tank size for a shoal of 4 Pygocentrus nattereri is 75 US gallons. The reccomended minimum tank size for a shoal of 4 Pygocentrus cariba is 85 US gallons. Add 75+85=160, then take 25% of 160 which equals 40. 160+40=200. You would need a minimum of 200 US gallon aquarium to house 4 Pygocentrus nattereri and 4 Pygocentrus cariba.
2. Large pieces of decor such as rocks or driftwood and areas of dense vegetation. Large pieces of driftwood can be bought at landscaping stores for a good deal. Large rocks equals heavy weight, so the artifical version of rocks may be a better idea for a glass aquarium to prevent any damage to the bottom of the tank, acrylic aquariums would most likely be OK though. Large pieces of rocks/wood mark out territories for the piranhas, reducing aggression. Dense buched vegetation such as various Vallisneria species, Ludwigia species, and other similar flora provide hiding and restings areas for piranhas to lurk around. These areas are vitally important to help prevent any possible deaths/injuries that may occur.
3. Frequent feedings. Frequent feedings are also very important because if a single piranha (or worse the whole shoal) becomes hungry the WILL eat the other Pygocentrus species if given the chance. Im not saying if you dont feed them 2-3 times a day your piranhas will be eaten, I am saying extended periods without food will set them off. Desperation doesnt settle in til about the tenth day without food, in desperation they will eat plants, bite equiptment, try to feed on hands in the aquarium, and attack the other shoal.
4. Equal number of specimens in each shoal. If the aforementioned desperation settles in, you dont want, say, 14 Pygocentrus nattereri and 3 Pygocentrus piraya in the same tank. The larger shoal will easily take out the smaller shoal as all Pygocentrus species grow to about the same size. If you had the same number of piranhas in each shoal, each specimen may have a fighting chance of life if fed in time. And if you have a tank of only one Pygocentrus species and desperation settles in, they will cannibalize each other. The problem also isnt so much desperation, just hunger. If the larger shoal goes for about 5 days without food theyll will take the easy kill to grab some food. So an important tip is you MUST have somebody to feed your piranhas while youre on vacation unless you want dead fish! And also monitor feedings closely, make sure every specimen gets at least some food during each feeding.
5. Same Size Specimens. People, use your common sense. If you're housing a shoal of 8 inch Pygocentrus cariba with a shoal of 1 inch Pygocentrus nattereri, do you think the smaller piranhas will be eaten? Sure will! Even if the smaller specimens are not small nough to be eaten, they will be bullied so be selective when choosing the size of your piranhas.
Shoaling Serrasalmus:
Attempting to shoal Serrasalmus species is EXTREMLY dangerous and should be only attempted by hobbyists with years of first hand experience with piranhas.
Serrasalmus do not actually shoal but rather loosely hang around each other, so dont expect full-on shoaling like you would from Pygocentrus nattereri. Only very few Serrasalmus can be shoaled successfully, these include Serrasalmus geryi and Serrasalmus compressus. It may be possible to shoal other Serrasalmus species, but the aforementioned species are the only species to have relative success. It should also be mentioned that Serrasalmus species can NOT be shoaled with different species, so only one shoal of one Serrasalmus species per tank.
The precautions for shoaling Serrasalmus include essentially the same concerns listed above. Obviously the "same number of species per shoal" part of number 4 isn't relevant for Serraslamus and the need for sufficient decor cannot be stressed enough. Additional precautions for Serraslamus include:
1. Tank Size. The tank size is a lot more leaniant for Serraslamus despite it being a larger risk. Take the reccomended tank gallonage for a single specimen, then multiply that by the number of specimens you want to keep (highly reccomended to house at least 3 per tank). It is possible to reduce that gallonage by up to 20% but this is not reccomended. For example, you want 3 Serrasalmus geryis, the reccomended tank size for a single specimen is 75 US gallons, multiply 75 by 3 which equals 225, then if you want to be risky reduce that number by 20% which is 45, 225-45=180. The minimum tank size for 3 Serrasalmus geryis would be 180 US gallons.
2. Monitoring each specimen daily. If one specimen looks ill/injured, the other specimens may attack it in hopes of an easy meal. Serrasalmus piranhas are expensive, so unless you want to risk losing one be my guest, but if you dont just look for signs of illness and injury. At the first sign of illness/injury immediately place them in a hospital tank. Treat the hospital tank with the proper medications, and hold them there at least one week after all injury/illness appears to have healed. Make sure they are eating and active before placing them back in the display tank.
There are also some nearly impossible situations...
Other, Non-Prihana Tankmates:
Did I mention that nothing can be SAFELY kept with piranhas? The risk of predation runs extremely high when non-piranha tankmates are involved. Its really best to not even bother.
Additional Links:
Piranha Keeping 101
Piranha Profiles in the Fish Index
Many thanks to pica_nuttalli who made this messy thread legible!
Questions pop up often about what tankmates could possibly be kept with piranhas. The final say is this: Nothing can be SAFELY kept with piranhas!
You constantly run the wisk of all tankmates being eaten if housed with piranhas and it is highly reccommended that all piranhas regardless of species only be kept in a species-specific tank. Shoaling species such as Pygocentrus nattereri must be kept in shoals, but everything other else is far better suited to live as the sole individual in the tank.
There are some risky, yet possible situations...
Shoaling Pygocentrus:
Before I start, let it be known that different Pygocentrus species will not actually shoal together; they will only tolerate each other. (I.E.: you cant put one P.attereri, one P. piraya, and one P. cariba together and expect them to shoal with each other, you need 3-4 specimes of each species for shoaling. If you keep 3 different species singly, they will just avoid each other).
It is possible to house different Pygocentrus species together in the same tank such as Pygocentrus cariba, Pygocentrus nattereri, and Pygocentrus piraya. This is risky, but considered "easy" if the proper precautions are taken.
1. A tank large enough to house a shoal of all species. Heres a guideline: Take the minimum reccomended tank size for shoal species A, take the minimum tank size for tak size for shoal species B, and if applicable the minimum tank size for species c,d, and so on. Add all of the minimum tank size together, then add AT LEAST 25% of that volume to the tank and you have a minimum tank size for housing different Pygocentrus species together. For example, the minimum tank size for a shoal of 4 Pygocentrus nattereri is 75 US gallons. The reccomended minimum tank size for a shoal of 4 Pygocentrus cariba is 85 US gallons. Add 75+85=160, then take 25% of 160 which equals 40. 160+40=200. You would need a minimum of 200 US gallon aquarium to house 4 Pygocentrus nattereri and 4 Pygocentrus cariba.
2. Large pieces of decor such as rocks or driftwood and areas of dense vegetation. Large pieces of driftwood can be bought at landscaping stores for a good deal. Large rocks equals heavy weight, so the artifical version of rocks may be a better idea for a glass aquarium to prevent any damage to the bottom of the tank, acrylic aquariums would most likely be OK though. Large pieces of rocks/wood mark out territories for the piranhas, reducing aggression. Dense buched vegetation such as various Vallisneria species, Ludwigia species, and other similar flora provide hiding and restings areas for piranhas to lurk around. These areas are vitally important to help prevent any possible deaths/injuries that may occur.
3. Frequent feedings. Frequent feedings are also very important because if a single piranha (or worse the whole shoal) becomes hungry the WILL eat the other Pygocentrus species if given the chance. Im not saying if you dont feed them 2-3 times a day your piranhas will be eaten, I am saying extended periods without food will set them off. Desperation doesnt settle in til about the tenth day without food, in desperation they will eat plants, bite equiptment, try to feed on hands in the aquarium, and attack the other shoal.
4. Equal number of specimens in each shoal. If the aforementioned desperation settles in, you dont want, say, 14 Pygocentrus nattereri and 3 Pygocentrus piraya in the same tank. The larger shoal will easily take out the smaller shoal as all Pygocentrus species grow to about the same size. If you had the same number of piranhas in each shoal, each specimen may have a fighting chance of life if fed in time. And if you have a tank of only one Pygocentrus species and desperation settles in, they will cannibalize each other. The problem also isnt so much desperation, just hunger. If the larger shoal goes for about 5 days without food theyll will take the easy kill to grab some food. So an important tip is you MUST have somebody to feed your piranhas while youre on vacation unless you want dead fish! And also monitor feedings closely, make sure every specimen gets at least some food during each feeding.
5. Same Size Specimens. People, use your common sense. If you're housing a shoal of 8 inch Pygocentrus cariba with a shoal of 1 inch Pygocentrus nattereri, do you think the smaller piranhas will be eaten? Sure will! Even if the smaller specimens are not small nough to be eaten, they will be bullied so be selective when choosing the size of your piranhas.
Shoaling Serrasalmus:
Attempting to shoal Serrasalmus species is EXTREMLY dangerous and should be only attempted by hobbyists with years of first hand experience with piranhas.
Serrasalmus do not actually shoal but rather loosely hang around each other, so dont expect full-on shoaling like you would from Pygocentrus nattereri. Only very few Serrasalmus can be shoaled successfully, these include Serrasalmus geryi and Serrasalmus compressus. It may be possible to shoal other Serrasalmus species, but the aforementioned species are the only species to have relative success. It should also be mentioned that Serrasalmus species can NOT be shoaled with different species, so only one shoal of one Serrasalmus species per tank.
The precautions for shoaling Serrasalmus include essentially the same concerns listed above. Obviously the "same number of species per shoal" part of number 4 isn't relevant for Serraslamus and the need for sufficient decor cannot be stressed enough. Additional precautions for Serraslamus include:
1. Tank Size. The tank size is a lot more leaniant for Serraslamus despite it being a larger risk. Take the reccomended tank gallonage for a single specimen, then multiply that by the number of specimens you want to keep (highly reccomended to house at least 3 per tank). It is possible to reduce that gallonage by up to 20% but this is not reccomended. For example, you want 3 Serrasalmus geryis, the reccomended tank size for a single specimen is 75 US gallons, multiply 75 by 3 which equals 225, then if you want to be risky reduce that number by 20% which is 45, 225-45=180. The minimum tank size for 3 Serrasalmus geryis would be 180 US gallons.
2. Monitoring each specimen daily. If one specimen looks ill/injured, the other specimens may attack it in hopes of an easy meal. Serrasalmus piranhas are expensive, so unless you want to risk losing one be my guest, but if you dont just look for signs of illness and injury. At the first sign of illness/injury immediately place them in a hospital tank. Treat the hospital tank with the proper medications, and hold them there at least one week after all injury/illness appears to have healed. Make sure they are eating and active before placing them back in the display tank.
There are also some nearly impossible situations...
Other, Non-Prihana Tankmates:
Did I mention that nothing can be SAFELY kept with piranhas? The risk of predation runs extremely high when non-piranha tankmates are involved. Its really best to not even bother.
Additional Links:
Piranha Keeping 101
Piranha Profiles in the Fish Index
Many thanks to pica_nuttalli who made this messy thread legible!
how long you kept piranha?also my lfs are selling baby black piranha are they what you keep?
my formatting skills suck!
i'm on the opposite end of you; i'm format obsessed 
