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FAQs on the Piranhas Behavior

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

Related FAQs:  Piranhas 1, Piranhas 2, & FAQs on: Piranha Identification, Piranha Compatibility, Piranha Selection, 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 nattereri 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.>

Juvenile red belly piranhas hiding     8/13/13
Hi, I have 4 red bellied piranhas in a 125 gallon tank.
<I would keep more than this or you will likely end up with just one. Six specimens seems to be a good starting point, just as it is with any other schooling fish.>
I have a mass of floating plants covering the top of the tank to help dim the light. The tank is also planted good. My question is why are the always hiding in amongst the floating plants at the surface all day long?
<What they do. Assuming they're not "gasping" at the surface because of water quality or chemistry issues (check!) then hiding among floating plants is pretty much what they like to do. If you buy Piranhas expecting them to be exciting fish, you will be sorely disappointed. Indeed, they are among the least exciting fish in the hobby. They are open river fish, and right out of the box hate being in aquaria. They are largely crepuscular in the wild, so don't do much during the day anyway, and when kept in small groups they are extremely nervous. The confines of the aquarium scare them even more, so overall, you have fish that don't want to be in a fish tank and make it very clear by their body language how they feel! For any aquarist who wants an exciting piranha, I'd always recommend Exodon paradoxus, a 10-15 cm/4-6 inch relative that can be kept in bigger groups with less hassle, is almost hyperactive in nature, but has the same feeding frenzy, even when offered flake!>
I Feed them frozen shrimp from shrimp rings, and alternate feedings with freeze-dried krill.
<I'd vary the diet a bit more. Crustaceans tend to contain a lot of Thiaminase, which means they contains relatively little vitamin B12. So choose something that doesn't contain Thiaminase and use that as well as the shrimps. Cockles are good, as are pieces of most white fish fillet (cod or tilapia for example). You are quite right not to use live feeder fish, there's no need and they pose a health threat, but fish fillet is generally taken quite readily. Some success has been had using fruit and seeds, which as I'm sure you know are a significant part of their diet in the wild (probably when meaty foods are scarce).>
They eat at times, but more so they just prefer to hide out all day long out of sight. I change the water 25-30% weekly, siphoning the gravel as I go. Should I be changing the water more (10-15% daily or every other day) to make them more active?
<Water changes are good, and small daily water changes are ideal. However, the trick here will be getting the balance between water changes and disturbing the fish, because each time you mess around with the tank, you'll spook these pathetically frightful fish. Move quietly and turn the lights of the tank off, but again, make it too dark and you won't see what you're doing, and when alarmed these fish can (and do) bite. Adding vertical rocks and bogwood roots, tall plants (e.g., Giant Vallis, real or plastic) will go some way to giving the fish more feelings of security, and in time, a bigger tank will help significantly (ideally one with a sump, so you can do water changes without putting your hands in a tank full of potentially dangerous and easily scared fish). Hope this helps, Neale.>

Piranha Health, Feeding, Behaviour - 10/18/2012
Hi, my name is John and I have a red belly piranha and I was reading and noticed it was a really bad idea to put feeder fish in there so I'm going to take them out.
<Very good move.  He will do much, much better eating meaty prepared dry and frozen foods.>
But I was wondering if it was too late for my fish friend. He is acting weird, he keeps swimming into my glass and stays on it for awhile looks like he is chasing himself or kissing it.
<This could just be normal behaviour, chasing/biting his reflection.... 
Without clear details about your tank (size, water quality, etc.), it's hard for us to know from a distance.>
He also will swim sideways and rub his side on the gravel.  Not sure why he does this.
<This could be bad news.  Test your water for Ammonia, Nitrite, Nitrate, and pH.  Ammonia and Nitrite must be ZERO, and Nitrate less than 20ppm.  If there is any Ammonia or Nitrite at all, or Nitrate is higher than 20ppm, do water changes to correct the problem.  If you can't test your water right away, then do a nice big water change anyway, just make sure that you dechlorinate, and try to match temperature and pH.  Piranha are pretty resilient, but do prefer soft water with a slightly lower than neutral pH if possible.>
Just trying to figure out why he does this all day then sits under my filter for a couple hours then he'll be at it again.
<As above, check your tank's water - or if you don't have test kits, ask your local fish store to test it for you and to show you the results.  As to why he just sits around under your filter, make sure your tank is suitably large for this very big, active species.  Also bear in mind that, although piranha are very aggressive, they are a schooling fish.  Without more of his own species to hang out with (and a VERY large tank to house him and his buddies), he's not going to act normally.  The flashing (turning on his side and scraping on the gravel) is disconcerting though, and suggests either a water quality problem or possibly a parasite or other problem brought in with the feeder fish.  Watch him closely for any abnormalities, especially signs of "Ick" (Ichthyophthirius multifiliis), a parasite which will show up as little white specks on the fish, and is often brought in by feeder fish.  Also, keep reading, on WWM and elsewhere, about piranha care, behavior, and disease.  Your pet is sure to thank you for informing yourself about him, and you'll enjoy learning more about this wonderful, toothy Serrasalminid.  Wishing you and your fishy pal well, 
Tyvm really appreciate it
<Glad to help.  Do keep reading, learning, and enjoying your fish. 

Piranha behaviors. 3/30/11
I have five piranhas in a 75 gallon tank. I've been noticing that they keep nipping at each other kind of like they are breeding, but I know that they are still to young to breed. I keep thinking that they do this for
territorial reasons but I'm not sure because they tend to be ok one second and fighting the next. What should I do or can you explain to me what they are doing
<Hello. What species are these? Red-Bellied Piranhas (Pygocentrus nattereri) won't form stable groups with fewer than 6 specimens, realistically needing 150 gallons or more for that to happen (allow about
20 gallons per specimen, given their adult size and need for a high protein diet). In smaller groups all that happens is the dominant one eventually kills all the others. This more or less holds true for other Pygocentrus species. Virtually all the other piranha species are solitary when mature, and only school together when young, and these must be kept singly, under home aquarium conditions at least. A common mistake with piranhas is to use live feeder fish, and these make piranhas even more aggressive than normal. Stick to pellet, fresh and frozen foods, including suitable "greens" as well, since all piranhas consume some plant matter in their diet. Hope this clarifies things for you. Cheers, Neale.>

Red (-Bellied) Piranha Hi there! I have 3 Red (-Bellied) Piranha, but they are all stressed. Every time I go near the tank, they all swim around and hit on the glasses. Even I feed them, I have to go away from the tank, otherwise they won't eat. why do they like that? Is there anything that I can recover them? Thank you <A few things would likely help here... providing more cover in the way of plants and driftwood... more circulation in conjunction with your filtration, and inclusion of some "dither fishes"... like other Characiform fishes and South American catfishes... as well as time going by, the tank being in a more public thoroughfare area. Bob Fenner, who says, we placed our Piranha piece's images last week on the www.WetWebMedia.com site, and took a few more pix yesterday at the Steinhart Aquarium... now need to flesh out the text for article and more inclusion>

Piranha's I have noticed that your piranha spec sheet is off a little. You can look at other websites to get a better understanding. It says that p. piraya is a max of 13 inches. That is a common Redbelly that can reach that size. P piraya can reach 20 plus inches. I am not trying to boast or anything like that. I just thought that I could help a little with your info. Also the piranha that is listed as p piraya is a red belly. If you want I can give you a correct pic to use on your site. It is one of mine, and no copyright infringement to worry about. I have learned a lot from this site and would like to give a little back. Thanks Alex <Thank you for the input and kind offer. Do send the Natterer's pic and I'll post it with credit to you. Bob Fenner on FishBase: http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=8696&genusname=Pygocentrus&speciesname=piraya>

Misinformation on the piranhas Hey Robert You have mis information on the piranhas the species piraya get bigger then 13 inches. They can get around 20inches <Thank you for this input... hmm, have kept this species of Pygocentrus... didn't realize it attained such dimensions... according to fishbase.org this piranha only gets to 34 cm. standard length: http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=8696& genusname=Pygocentrus&speciesname=piraya What leads you to believe (reference, personal experience...) that this fish grows to fifty centimeters? Bob Fenner>
Re: Mis information on the piranhas
Hey Robert Because I have personal seen two that were 14 and 15 inches. <Will post your observation as such. Bob Fenner>
Re: Mis information on the piranhas
Hey I hope you dint take offense to my email. <No. "What comes is acceptable". Bob Fenner>

Red belly piranha I have a red belly piranha. I have had him for about 3 weeks he is about 3 1/2 -  4 inches. I came home and he was sitting sideways looking at the top of the tank like he was dead but when I touched the plant he was moving again what is the problem  <Hi there. Red Belly Piranha are pretty messy fish, and they quickly foul water unless you give them a large tank with plenty of filtration. They are used to living in a river system with constant fresh water flowing. I would test the water levels and make sure that the ammonia and nitrite levels are okay. Then add powerhead to increase current, also airstone and air pump to add the needed oxygen. I also suggest you check out websites like www.piranhafury.com, there are many piranha owners there that can help you enjoy your pointy toothed little fish. good luck. -Magnus>

Piranha Illness  10/2/05 Hi! I have a Red-Bellied Piranha that I have had for 5 years. He has done well up to this point. Just recently, I've noticed that he has been swimming on his side and upside-down. I was afraid that he might have something like gill flukes. I'd hate to have him die if I can do something about it. Thanks! <Mmm, not gill flukes or any pathogenic/biological cause unless you've introduced the vector through feeding contaminated food/s. More likely environmental... I would (very quickly) check your water quality and whatever it shows, start large daily water changes (like 30%) with water that this fish lives in (soft, acidic, low nutrient load, warm). Bob Fenner>

Piranha Shedding? 7/27/05 I have 5 red bellied piranhas in a 55 gallon tank <A wee bit overstocked there, are we?> and they were all doing very well until about two days ago when one of my piranhas got big dark spots near his head and looks like he is shedding his skin is this a bad thing. <Quite possibly so. Sad to say, I have absolutely no idea what it is. However, as you know exactly what it looks like and have an image (your fish) for reference, it should be decently simple to locate the disease and accompanying treatment info within the following links: http://www.wetwebmedia.com/tanktroubleshting.htm http://www.wetwebmedia.com/tanktrb2of2.htm http://www.wetwebmedia.com/FWSubWebIndex/fwdis3setsfactors.htm http://www.wetwebmedia.com/FWSubWebIndex/fwfshparasites.htm http://www.wetwebmedia.com/FWSubWebIndex/fwinfectdisfaqs.htm http://www.wetwebmedia.com/FWSubWebIndex/fwfshparasitefaqs.htm http://www.wetwebmedia.com/FWSubWebIndex/fwinfectdisfaq2.htm Good luck, and I hope he pulls through!> thank you Anthony <Mike G>

Red belly piranha, hlth., beh.   ~ 01/12/09 Hello I was wondering if you could help me with a worry of mine. I have four red bellies about 5 in in length and they have been doing fine up until about 4 days ago. They are acting normally but they lose their vibrant red bellies at night I never noticed it before maybe it's been that way at night but I never noticed it. Their water temp Is maintained at 82 F and their water ammonia and nitrate levels are normal. I did however take out a piece of driftwood that sit in the middle of the tank but they were too big to swim into it so they never used it. Any ideas? Joel <Joel, it is perfectly normal for Pygocentrus nattereri to change colour at night. They also change colours as they mature. It is quite possible that they've always had different colours at night, but they're getting to an age now where these differences are become more pronounced. You're keeping your fish a little on the warm side for this species, though piranhas from the rather warm Rio Xingu do indeed like things a bit hotter than otherwise. If you turn down the thermostat a notch, not only will there be more oxygen in the water, but your fish will also live longer and be less aggressive towards one another! The 23-25 C, 73-77 F is just fine for them. If in doubt, visit Fishbase to check the temperature preferences of your fish; for some reason I cannot fathom, a crazy proportion of aquarists keep their fish far too hot, wasting money and compromising health. For what it's worth rather than worrying about bogwood, use plants to provide shade for these light-phobic fish. Tall plants, such as giant Vallisneria and big Java ferns are ideal, and floating plants with long roots like Amazon Frogbit work very well too. Piranhas are primarily dusk/dawn fish, and they despise bright light. Cheers, Neale.>
Re: Red belly piranha  ~ 01/12/09
Thanks Neale I appreciate the help! A lot of websites for piranhas suggest 80+degrees but I see the logic in your explanation. This might be a silly question but is it at all possible for a red devil cichlid to cohabit a large enough tank? And if so what size is needed for such a thing? Joel <Hi Joel. There are very few Piranha web sites I trust. Too many people keep these wonderful fish badly. Like Rottweilers and pit-bull terriers, they have this image of brutality and so brutal people end up keeping them. But just like those dogs, kept properly, Piranhas are fascinating and rewarding pets (as well as very beautiful, in their way). Anyway, one of the best sites is the Oregon Piranha Exotic Fish Exhibit site, a semi-academic site with a ton of good information. Here's their Pygocentrus nattereri page. They report wild fish tolerating remarkably cool conditions, for short periods at least, but do recommend low 20s C (low to mid 70s F) as the optimal temperature, and this meshes with what Fishbase reports too. By the way, don't change the temperature all at once, but just knock it down a degree every couple of weeks, and watch how your fish react. http://www.angelfire.com/biz/piranha038/nattereri.html Now, as for tankmates. I have seen Piranhas cohabit with Convict cichlids, but what we see in these situations tends to be a dominant cichlid that terrifies a small group of Piranhas. Because Piranhas are nervous at the best of times, I just don't see any mileage in that, and would recommend keeping the Piranhas on their own. Sometimes Suckermouth catfish like Plecs coexist, but that usually depends on the Plec being their first, so the baby Piranhas grow up with it, accepting it as part of the furniture (rather than food!). Adding a catfish to an established tank is just too risky, and I don't need to tell you that Piranhas have a lot of firepower at their disposal should they decide to turn on a tankmate. When all is said and done, my advice is to keep 'em alone. A nicely decorated Piranha tank is a thing of beauty, just as it is. Cheers, Neale.> Re: Red belly piranha Thanks for all the help Neale you've helped a ton Joel <Happy to help. Cheers, Neale.>

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