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FAQs on the Piranhas Selection

Related Articles: Piranhas, Serrasalmine Fishes, Characoids/Tetras & Relatives Feeding Feeder Goldfish,

Related FAQs:  Piranhas 1, Piranhas 2, & FAQs on: Piranha Identification, Piranha Behavior, Piranha Compatibility, Piranha Systems, Piranha Feeding, Piranha Health, Piranha Reproduction, & Piranhas and Relatives, Feeding "Feeder" Goldfish, Pacus, Silver Dollars,


need help on forum please. RB Piranha social issue    /RMF     9/25/16
<Hello there>
I have 3 red belly piranhas, I have had them 8 months with no problems until now. I have a tank full of caves and full of plants like there natural habitat. each fish has there own cave they stay in.
but the last 2 days one of them is now staying next to the heater and every few hours I can hear him smash around, I'm presuming accidently touching the heater?
<I'd cover this heater (perhaps with a perforated plastic pipe) to prevent damage to both it and the fish)>
was wondering why he would leave his cave and move to the heater area?
any help is greatly appreciated.
<Likely this is a situation in which there are too few individuals of this Piranha species in too small a volume. Take a look on the Net, pix in the wild... Serrasalmus natteri lives in large schools in huge volumes; and is almost too skittish in captivity to do well... Needs several specimens, hundreds of gallons of space.

Let's have you read here:
and the linked files above. Bob Fenner>
need help on forum please. /Neale      9/25/16

I have 3 red belly piranhas, I have had them 8 months with no problems until now. I have a tank full of caves and full of plants like there natural habitat.
<How big is the tank? This is important, as will be explained...>

each fish has there own cave they stay in. but the last 2 days one of them is now staying next to the heater and every few hours I can hear him smash around, I'm presuming accidently touching the heater?
<Possibly. Piranhas are active, but mostly when the lights are off.
Technically, they're "crepuscular" fish, active at dawn and dusk. They are relatively inactive during the day. So while they look like they don't do much when you're watching them, at certain times they are a lot more active. Sexually mature males are also territorial, and will be aggressive towards other males. It's difficult, probably impossible, to keep fewer
than 5-6 specimens together as adults. I'm sure one or two people have gotten lucky (they may well have had mostly or all females) but for the most part Red Bellied Piranhas should be kept in groups of at least six specimens. That requires a fair amount of space; I'd suggest 350 litres/100 US gallons as the minimum.>
was wondering why he would leave his cave and move to the heater area?
<It could be territoriality, as discussed above. In larger groups the territorial behaviour is easier to manage because one fish cannot become dominant as easily.>
any help is greatly appreciated.
<The classic solution to this sort of social behaviour problem, e.g., with Mbuna, is to add extra specimens, but Piranhas are cannibalistic and aggressive, making this approach extremely challenging. Probably the safest approach would be to remove all the Piranhas, rearrange all the decorations, add new specimens of similar or larger size, and then reintroduce the original specimens. But even then there's a big risk of aggression, especially if the tank is too small. Cheers, Neale.>

Piranha; stkg., comp.     3/4/16
Hello crew
I am restocking my 90 gallon with predators to take care of my surplus of feeders that I breed. I was thinking red belly piranha with a school of Exodon paradoxus. Thoughts?
<Much as I like Exodon paradoxus as a vastly better aquarium fish than Serrasalmus and Pygocentrus spp., the two types of fish don't cohabit. Larger piranhas will always be a potential predator on smaller fish like
Exodon, but conversely, Exodon are boisterous and nippy enough they could threaten the much more nervous and easily startled piranhas.>
Is this possible?
What are my other options here for toothy predators?
<Rocks, plants, plastic skulls, that sort of thing. The reality is that piranhas are not good aquarium fish, their sensitivity to poor water quality and their inherent nervousness making them much less adaptable than their Hollywood image might suggest. Like other experienced aquarists I've seen piranhas living with Plecs and even convict cichlids, but these situations are memorable because they're exceptional. Piranhas are simply
better kept singly (if a non-schooling species) or else in the largest possible grounds (for the more sociable species). If your tank has space, either relish the fact water quality management is easier or increase the
size of the school of piranhas you're keeping (with the usual caveats about only combining the same species and similar sized specimens). To be clear and re-state the central message here: a piranha aquarium is a dull
aquarium, and your piranhas want it that way. They're basically boring fish that need a dark, quiet aquarium to be happy. Now Exodon paradoxus, on the other hand, is far from boring... though they can't really be combined with anything else, and you do need at least a dozen, and probably twenty or more, if you don't want them to kill each other!>
<Most welcome. Neale.>
re: Piranha     3/4/16

So scratching that idea are there any other good predatory fish that can work here? Wolf fish? I have kept most oddball fish and currently have a lot but nothing with actual teeth.
<It's not really a question of skill, but rather the fact Piranhas make terrible co-habitees. Even if kept with something they wouldn't kill, they're so easily spooked the Piranhas become stressed and more prone to
the sorts of behaviours that cause physical damage to each other or their tankmates. Invertebrates are obviously an option, snails, crayfish and things like that, assuming they're not bite-sized (so not Cherry Shrimps).
Such animals aren't really on the menu for Piranhas, and being slow-moving, they're don't spook the Piranhas. Of course you will see some of the Piranha forums recommend Plecs and Thorny Catfish, but often with a comment along the lines of "luckily these catfish are cheap in case something goes wrong...". Not sure the poor catfish would be quite as phlegmatic! Ditto big but docile cichlids such as Oscars. So really, advanced aquarists
simply accept the fact Piranhas are dull and work around it. It's never going to be a fun tank, but it's a specialist tank for studying these undeniably interesting characins. But if you're after an interesting oddball aquarium, well, that's another tank... make sense?>
<Most welcome. Neale.>
re: Piranha     3/5/16
What would a good predator be for this tank to take care of the surplus?

<I'm not sure what you're asking here. If you're breeding killifish or livebearers in another tank and have ridiculous amounts of fry, then an obligate piscivore like a South American Leaffish or Pike Livebearer in its own tank might be one option, though you'd need a very, very stable supply across many years to keep these types of fish. If it's just the odd batch of cichlids or Corydoras you're breeding, then just pass them on to your
local shop or aquarium club? Ditto if you've got surplus piranhas then you could surely sell them? And to be clear, I'm 100% against the idea of keeping predatory fish simply to stage "fights" where one fish eats
another. It's neither a good way to keep piscivores (increases aggression; exposes them to pathogens; not nutritionally balanced) nor ethical (causes stress and suffering in the prey). Cheers, Neale.>
re: Piranha     3/5/16
I have a large amount of live bearers.
I didn't realize that they would breed so quickly and I cant do anything else with them. Thanks
<Got you know. Then something like an African Butterflyfish might be an easy to obtain choice, but South American Leaffish would be a great companion for these and really interesting to keep. You'd need to supply
the Leaffish something like a dozen half-inch fry a week, and they generally eat nothing else besides tiny fish, so you really do need a production line of livebearers! African Butterflies will eat any fry they find, but also take wingless fruit flies and other small insects easily obtained from reptile shops, so they're much less difficult to keep. Some will even take decent flake and pellets too. Cheers, Neale.>
re: Piranha     3/5/16

Ok. Once again thanks for your help neale!
<Glad to help. On reflection probably underestimated the amount of food needed for Leaffish, to be honest. Don't need feeding every day of course, but they'd probably get through half a dozen half inch fry in one sitting,
perhaps three or four times a week. Oh, and do look at Leopard Bushfish too. Lovely fish. Cheers, Neale.>

Piranhas   2/2/15
Quick question, I have 3 juvenile red belly piranhas in a 80 galloon bow front, I also have 1 adult red belly in a 29 galloon.
<What's a galloon?>

I do feel bad that the adult just sits in his cave(s) and is lonely and doesn't have another buddy. I wanted to hear you're opinion if I could stick the adult with the 3 juveniles in the 80 galloon. Would it be safe?
If not than that's fine It's better to be safe than sorry.
<Depends on relative size... if more than an inch, I'd not mix. Even IF all the same size; will at times bite chunks out of each other. Bob Fenner>

Piranha anyone?  Sel., sys.    3/18/10
A few weeks ago I tore down my African cichlid tank (found a new home for them all) since I had decided to take on the challenge of having Piranhas.
<Challenge is certainly the word. These are quite difficult fish to keep well.>
I find these are exciting and beautiful fish to have and legal in the state of Maryland.
<Honestly, I think a lot of people find the concept of Piranhas rather more exciting than the actual fish. Let's be clear about what these fish are like. Most days, they sit around doing nothing. They are extremely nervous fish and never really become "tame" in any meaningful way. At best, they're merely scared rather than terrified. They're crepuscular fish, meaning they're really only active during dusk and dawn, and won't to anything much when the lights are on unless there's plenty of shade (e.g., Indian Fern).
Feeding them isn't difficult, though the whole live food aspect is overdone and misunderstood. Setting aside the thrill teenage boys get from throwing live Goldfish (or worse, mice!) into the tank, Piranhas are correctly maintained on fresh or frozen foods, never cheap feeder fish. They don't need daily feeding, so half the days of the week these fish do precisely nothing, unless of course you prefer to feed smaller quantities daily. Like all carnivores, avoidance of Thiaminase creates problems if you don't research food items carefully and balance those foods that contain Thiaminase (like prawns) against a greater quantity of foods that don't (like tilapia fillet). Very few species are gregarious *once mature* and even the social Pygocentrus spp. are temperamental in this regard, and more often than not aquarist buy a group but end up with a singleton. Since it's really a gregarious fish, being kept in solitary means it is EVEN more frightened than the average Piranha. For a group of six Red-bellied Piranhas -- the minimum number for which you have a better than 50% chance of a stable grouping without serious fighting/death -- you need not less than 450 litres (about 120 US gallons). Filtration needs to be top-notch since all Piranhas expect high oxygen content and zero ammonia/nitrite levels. While not precisely delicate fish, there is some variation among species in terms of things like tolerance for copper, so mortality can be high if you don't know precisely what you're doing. In short, apart from their reputation, these fish have almost nothing going for them as pets. By
every objective measurement they're poor choices for the home aquarium.>
My tank is 90 gallons and has 2'' ferrite soil with a gravel top, various live plants, and three awesome bogwood logs that look like they just came straight out of the Amazon. Two Fluval 405's and two Whisper EX70 hang-on
power filters, of which one is currently employed, and a Koralia 4 power head to keep the water flowing through and around the bogwood. The LFS received a large shipment of juvenile (2") red bellied Piranha (P. nattereri).
<Very small specimens, paradoxically, are often the most vicious towards each other outside of spawning adults, even though wild piranhas are gregarious. So watch them carefully, and look for signs of biting, missing eyes, etc. When setting up a group, the best size to go with is the subadult, around 10 cm/4 inches. That's about the size of Silver Dollar fish.>
My question is how many can I stock (I'm thinking 5)
<Not enough. Five Red-bellied Piranhas = One dominant Piranha, and four dead Piranhas.>
in my tank based on the current set-up? I have done a lot of research on OPEFE since Bob mentioned them in one of his postings, and that is a great site for learning about this species. I don't want to get too many and I don't want to get to few of them either.
<You need at least 6, realistically 8 or more, for a stable group.>
I do have moderate lighting for the plants but there is also a lot of "shade" from the bogwood logs,
<They don't use logs. Must be floating plants. The shade MUST be above them, not on the ground. These are midwater characins, not catfish.>
would this be ok or do I have to lesson it a bit (160 watts)? Also, can you have an algae cleaner in there or will it upset them?
<Look, you're lucky if they don't bite you when you're cleaning the tank.
Seriously. Happens all the time. Think a catfish is going to work...?
My tank has been up and running now for a few weeks without fish.
<Look instead at Exodon paradoxus, a far more active, and far smaller, schooling characin that has better colours but the same "feeding frenzy" behaviour. In your tank you could keep 20 specimens without problems.
They're fantastic fish, and will go into their feeding frenzy every day just for flake food, let alone tidbits of fish fillet or bloodworms. I don't mean to squash your hopes, but Piranhas really aren't good pets, and you can quickly end up with a big, expensive tank filled with boring fish.
Cheers, Neale.>

Piranhas 'still illegal in California  12/9/05 Hi <Hello.> Just wanted to know if you know anybody selling the piranha I'm trying to locate but still having a hard time to find one. I live here in California. <Ahh'¦bingo, all species of piranha are illegal in our Golden State here 'both to sell and own. But on the bright side you can't beat the weather here. I'm enjoying this 65 degree winter.> and really wanted to get the red. Pls send any info at XXXX@X.XXX <Sorry I could not be of more help, Adam J.>  <<Be smart, go with Pacu.  They look a lot like piranha, are nowhere nearly as difficult to keep, and are fun to feed big bugs to.  Marina>>

Getting Piranhas  - 01/03/2006 I have a 30 gallon tank, all set up.. I will be ordering red bellied piranhas at 1 inch in length, I know they do better in shoals, but how many (at this size) would be best to put in the tank? I want an active tank, and as they grow, their tank size will also become larger. Also.. should I buy them at 2 inches instead of 1 inch, to insure stronger fish? thanks a lot-Matthew p.s. where can I make a donation to your site? It has been super helpful!! <Piranhas do better in groups. Alone they hide and really don't display much. I would get the one inch fish because this will give you more time to get the bigger tank. I have seen these fish up to a foot long. At this size they are less active. Six to these guys in a 75 to 100 tank would be fine with proper filtration and water changes.-Chuck>

Urban Myth In The Making! (Krikey, there's a toothy tetra in me loo!) A friend of mine is having trouble with her septic system. she was told if she gets a piranha and put it in her system it will clean it out I have never heard of it. <Umm- no offense to your friend- but this is one of the kookiest schemes I've ever heard of! First off- a septic system is no place for any living creature to reside in! Second- Releasing any non-native species into a domestic water source is both immoral and definitely illegal! Last, but certainly not the least- why in the world would she even think of using a piranha, of all fish, in such a capacity? I'm sure that the Yellow Pages in her area has a number of listings for septic system maintenance people, that do not use piranhas, divining rods, magic crystals, or psychic powers to do the job!> If there is any info on this could you send it to me. this is a real question- I would like some help. <This is a real answer- have your friend call a professional septic system maintenance service!> Thank you very much. deltadawn <You're a good friend for taking all of my abuse- but, seriously-do have her call a professional to solve her problem! Scott F.>

Piranha in Septic System  - 02/15/07 Hello:  I thought I'd offer some insight into the apparently wacky question posed by someone whose girlfriend had been advised to "put a piranha in her septic tank" to make it work better.  There is a commercial product called a Piranha system which is used to improve the performance of septic systems.  It doesn't use piranha fish (duh!), but rather a culture of bacteria that aggressively eats up stuff that plugs up septic systems, hence the name of the product.  So, the person's girl friend actually got good advice, just needs to distinguish between the fish and the septic system product.  (Kind of like a Plymouth Barracuda isn't something you go trolling for.) <<Ha! Thank you for this clarification. Lisa.>>

RB Piranha comp.   - 04/20/07 Hi Bob, <Well, it's actually Neale, but Hi anyway!> My son purchased some red bellied piranhas (Babies). <I trust he bought a book about piranhas first? These are neither easy fish nor ideal fish for beginners. They are also rather large and basically boring pets. Great for people with space and experience, but terrible for children.> However two smaller ones keep attacking the larger one. <Absolutely normal. As any book about piranhas will tell you, these are intensely hierarchical schooling fish that live in swarms of hundreds of specimens. When kept in twos and threes their normal behaviour is short-circuited and the dominant fish *invariably* ends up bullying the one at the bottom of the social order. This is repeated as each fish below the "boss" dies, until you have a single specimen. Being schooling fish, they are very unhappy kept alone, and this singleton is nervous, flighty, and not at all entertaining.> First time they ate his fins, tail and took out an eye (hence his name eyeball). I got a divider so that eyeball could recover which he did. Today however, the two smaller ones again attacked eyeball eating his fins and tail. Eyeball can not stay in an up right position, so again I put in the divider and have eyeball suspended in a net in an up right position. I have kept him alive now for 11 hrs, but was wondering how long I should keep him in the net? <Well, piranhas heal very quickly when in good condition. They have to: their mating rituals (if you can call them that) involve biting chunks out of each other. But as should be glaringly obvious, there's no way that "Eyeball" can ever be kept in the same tank as the other two specimens. Oh, and it's probably a matter of time before they fight. So be sure and get three large aquaria set up, one for each piranha.> Should I keep him there till I see signs of re growth of his tail? <Yes. And also when the wounds are nicely healed. And I'd keep treating the water with something anti-microbial, such as Melafix.> I feed them plenty (shrimp, fillets, snails, krill etc...) just do not understand why they attack eyeball. <As said above: from being kept in appropriate numbers. They are doing what comes natural.> All the fish are healthy otherwise.. At this point I do not want eyeball to pass away (so much work has gone into keeping him alive) water conditions are right on target.. Not sure if keeping him in a net in the up right position is the best idea, but at least he is not laying on his side on the bottom of the tank. Any suggestions on how I can help him heal quicker so he is not confined in the net but is still up right? <Sounds to me you're doing the right things in terms of triage. But keeping him in a hospital tank is probably the best route, and actually inevitable really because this fish will have to be kept apart from the other for the rest of its life.> Thank you so very much for having a wonderful site for people to use as a reference. <No problems. Glad to help. Now please, sit down with your son and discuss the future. A "safe" number of specimens is 4 in a 75 gallon tank. You can keep more than that, adding around 20 gallons per specimen. If this isn't on the cards, then your son may need to think about re-homing these fish. If he wants something piranha-like, Exodon paradoxus is easy enough to obtain, but smaller, and just as fierce; it's also prettier and more active, and will even eat flake. Finally, please make sure he isn't using live feeder fish for food. That's a sure fire way to introduce parasites and pathogens. Goldfish and minnows also have serious nutrition problems because they contain Thiaminase. The only safe feeder fish are livebearers bred at home. But with piranha you don't even need those, and your fish will be healthier given a pellet/stick staple diet carefully balanced to have all the nutrition fish need. Augment periodically with "treats" such as frozen silversides and lancefish. There are plenty of good books about piranha, and as a good mother it's up to you to teach your son about research and responsibility. Too many young boys buy piranhas because they are "scary" and then suddenly discover that, like all animals, they have needs and must be cared for properly.> Dar

My new tank, poor FW mix of lvstk., ich   1/31/08 hi, Currently I have 55G tank which contains four 2inch gold fish , six 2inch koi carp , two 4inch koi carp , six 2inch angels and one 25cm Pleco. I know it's a small tank ,that's why I am building a new 200G tank. <Very good.> I am thinking about buying 2 red bellied piranha. Is that a good idea?. <To mix with these fish? Absolutely not. In addition, most of the common piranhas in the trade, including Pygocentrus nattereri (the Red-bellied Piranha), are essentially solitary fish in aquaria. Their social behaviour in the wild is extremely complex and difficult to replicate in captivity. Juveniles may school together, but adults only form schools under certain conditions, and when mature the males are territorial and ultimately guard nests and eggs. Unless kept in BIG aquaria where there are AT LEAST SIX specimens, piranhas simply don't work in groups. The dominant male systematically harasses and eventually kills the other fish. The flip side to this is that single piranhas are nervous and scared of their own shadows! They are very VERY boring pets.> Is there any kind of fish that I can add with the piranha's? <None.> Right now I have one more problem , one of my koi carp is scratching ,what should I do . <Likely Whitespot/Ick and should be treated accordingly.> Is it necessary to remove live plants before adding any medicine into the system?. <Not normally, no.> One of my koi carp has full red body with small white patches in the middle, is that what u call white spot disease. <Sounds like it.> And last I want u to suggest a suitable filter for my new 200G tank (please mention the company name also) <The ideal filter will vary. If the tank contains just fish and no plants (or maybe floating plants or plants attached to wood) then an undergravel filter can work very well. Use at least two powerheads to get a gravel bed this size working properly. Alternatively, you can use one or more external canister filters. These work better with tanks that contain plants. In either case, the brand of filter doesn't matter much, though some brands, notably Eheim, have a good reputation for reliability and value over the long term. The main thing is turnover. For large fish like yours, you want the powerheads or filter pumps to produce at least 6 times the volume of the tank in turnover per hour. So in your case, the pumps should add up to 6 x 200 = 1200 gallons per hour.> thanks a lot Mathew <Cheers, Neale.>

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