Piranhas and Pacu (Oh! MY)
Robert:
<Anthony Calfo in your service... Bob has superglued himself to a piece of coral...strike one on his first foray into coral propagation>
Thought I would give you an update and ask you a few more questions, if you don't mind. It's been over 6 weeks since I've had the tank set up and the Piranhas are doing fine - despite the fact that I have yet to get the pH down to their ideal range: 6.5 - 7.0 The tank has reverse osmosis water in it so it's very soft (85 ppm) so I would think that the pH would adjust fairly easily, yet it won't go below 7.6! 
<what is the total hardness of the water coming out of the R/O unit and has this number been confirmed with another brand of test kit?>
It's a mystery to me why the pH won't budge. 
<85ppm is soft...but not extremely soft assuming that the test kit is accurate and not reading a bit low (which could explain the resistance)>
The tank has been up for a while now and according to what I've read, all established tanks will see a decrease in the pH levels as this is a natural process. 
<agreed and inevitable for most>
I've also read that the softer the water, the less buffering and therefore the easier it is to adjust pH levels. 
<yes>
Maybe 6 weeks isn't long enough and maybe 85 ppm is still too hard of water. Any ideas on what's going on?
<you are correct on both counts...but don't be obsessed with the low pH and soft water unless you are trying to breed them. The other side of the coin is that very soft and very acidic water is VERY unstable and quite frankly dangerous with the slightest slip in husbandry (overfeeding, delayed water change, etc)>
I'm going to be setting up an 125 gallon soon and will have a Pacu in that tank. 
<the tank is still not big enough...quite frankly, I hope that you don't buy the fish. It's an inappropriate animal for most tanks growing to over two feet in length. Cruel to let it stunt and die prematurely (a few years old) as most do>
My research indicates they like the pH levels even lower: 4.8 - 6.5!
<too dangerous for captive aquariology unless you are research strict about maintenance>
If I can't even get my 55 gallon to a neutral pH...how am I possibly going to get an 125 gallon to a pH level of 4.8 - 6.5 ???
<my friend, have you considered drinking alcohol? Relax, goombah. A pH around neutral is safe and reasonable for such hardy fish and will serve you well considering the waste load they produce and potential for disaster at low pH/unstable soft water. If you are willing to go to such great lengths for water quality... breed wild caught discus instead and at least make money for your pains...hehe. Kindly, Anthony>
Travis  

Follow-up to Piranhas and Pacus Oh My!
Anthony:
<You got Steven pulling his shift answering some of the daily mail.>
Thanks for your input...I appreciate it! Can you tell I'm just a tad on the obsessive compulsive side? he he I'm glad to hear that I don't need to be so worried about the pH levels and can relax a little. I do have a couple follow up questions on the Pacu. Don't these fish grow to the size of the tank? From what you're telling me they'll just grow and grow and grow until they basically die (if the tank is too small).
<It is not quite true that fish grow to the size of their tanks. Freshwater fish are a little easier to stunt their growth, but that is not healthy at all. How would you like to live your whole life in your closet? Get the picture.>
How big of a tank do you need for a Pacu?
<For any large fish, find the maximum length. The tank's width should be twice the maximum length of the fish and the tank's length should be four times the maximum length of the fish. And remember that this is a minimum. For a Pacu, 4 foot wide and 8 foot long and probably 2 or more feet deep.>
I'm not necessarily "married" to the idea of getting one so I'm open to alternatives. Can you think of any? The Pacu is the exact kind of fish I'm looking for: a freshwater fish, grows very fast, grows very big and won't attack you if you put your arm in the tank! I've tried Oscars in the past but had terrible luck with them as they always got some kind of disease (ich, hole-in-the-head, etc.). I can't think of any fast growing, large freshwater fish other than Pacus and Oscars so that's why I thought I would consider a Pacu. Any suggestions?
Travis
<Generally, Oscars are a great fish as long as you keep their water clean with frequent, large water changes and good filtration, house them in an appropriate sized tank, and feed them a varied diet (no feeder fish). There are many other cichlids that meet you request, but they all have the same captive care requirements as above. Kind regards, Steven Pro>

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>

Enough Oxygen in Piranha Tank?
I have a 120 gallon "high" tank (22-24" high and 5' long). I have 5 Piranhas in the tank and the water is set at 79 degrees. I use 2 AquaClear 500 filters and a Magnum 350 canister for continuous polishing. I also have a Hagen Powerhead (model 900 something) that turns about 400 gallons per hour. I use the power head for current only. I have the power head on a timer. It's on for 30 minutes, off for an hour, on for 30 minutes, off for an hour, etc. for each day. I know it's harder to get good oxygen in warm water
<Correct, but 79 is not too hot, just about right.>
just want to be sure my fish are getting enough oxygen. And how can you tell if you're not...do the fish become lethargic or something?
<Yes, become lethargic, stay at surface gasping for air.>
2 of my Piranhas always stay about 1/2" from the top of the tank in the corner while the other 3 stay at the very bottom. Not sure if this is due to oxygen levels or not. Any ideas? Travis
<Could be territorial disputes. Oxygen levels can be verified by test kits. Also, look at the other regular parameters; pH, ammonia, nitrite, & nitrate. -Steven Pro>

Piranhas in a 55gal.
hello, I have a 55gal. tank and have two 2.5inch piranhas and want to add more. I was wandering how many I could add if any, and if I should take the two piranha I have now out and put them back in with the new ones. what do you think? john
<I really like this group of fishes (a subfamily or family of what we generally call tetras or characiform fishes, the Serrasalminae or Serrasalmidae), but in order to give you more of a definite answer I need to know the species we're talking about. Please read here: http://www.wetwebmedia.com/FWSubWebIndex/serrasalminae1.htm
As you can see some Piranhas get quite large, and some species are much more difficult to keep together in such a small volume as yours... The time to add any is when they're small for sure, and all the same species, about the same size... Bob Fenner, who wishes these fishes weren't outlawed in California.>

Crowded Piranhas
When baby piranha starting getting bigger and older; I have the tank well planted and plenty of hiding spots for the fish. Now the Piranha are developing the Red characteristics, should I remove these hiding spots? The rock takes up a lot of room and it used to house 4 piranhas, now it could probably do 1 or 2; I am worried about the fish fighting with each other, what should I do?
<<I don't know the size of your tank but I'm guessing it's fairly small. The safest course of action would be to get down to 1 or *maybe* 2 fish. Ronni>>

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 Systems
Hi, I have recently bought some piranhas, they are all about 2-4 cm and I think they are red-bellies (they are silver with black spots and red bottom fins).
<Likely this species or Pygocentrus piraya>
I read questions on your site and just wanted to know if my conditions are ok and what to do to improve the health of my fish (having read the lack of understanding many people have of them I am keen to get it right and be able to take full care of my fish). For a start I have a 62 litre tank (is that about 16 gallons?) with 6 piranha of the size I said.
<Yikes... this is a way too small volume for this number of fish... even when small you will find them chewing each other up substantially... eventually killing all but one... This number of piranha really should ultimately be kept in a system about ten times this size>
I'm feeding them frozen bloodworm and brine shrimp, lately I have been feeding them more than the shop owner's recommended half a cube a day because they bite each others' fins.  I have lots of real and fake plants in the tank, as well as some fake tree roots ( I read they like lots of cover)...
<Yes>
...and a skeleton that bubbles. I have a heater at 77*F and filter (I say simply filter because I don't quite understand biological and mechanical filter and all that)...
<Oh, simple to grasp...>
...it is one that sits in the tank and pumps the water with sponges in the middle, in that I have nitrite removers and a bag for
algae removal. I use Nutrafin cycle and Plus to keep the water hardness and stuff right, I also have ph balance to keep it at 7.0. You should also know that I have two Plecos (catfish) in the tank that eat algae and mind their own business, the bigger piranha sometimes try and bite them but they have tough skin and are at least 5cm so the piranha leave them alone. I would GREATLY appreciate any advice or any change that you would suggest. thanks
<Principally larger quarters... do plan on moving these fishes to a bigger tank... SOON... and I would add another outside power filter (either hang-on or canister)... for added filtration and circulation... These are gorgeous fish, and you can look forward to enjoying them for many years with good care. Bob Fenner>

Re: piranhas
Hello, thank you for your guidance!, I will increase my tank size very soon.
could you help me with one last thing please. I want to start feeding the fish some meats to bring out their natural hunting instincts etc.. but I read its not good to feed the fish meat like beef heart but instead raw prawns and salmon.
<Actually, some beef heart is not a problem... I had piranhas of a few species for several years and fed this along with other meaty foods>
I saw some raw prawns at my local supermarket, are these ok?
<Yes>
because I know food for human consumption is packed with preservatives and chemicals (and crap). If not where would be the best place to get theses foods? thanks again.
<Bait shops, earthworms from your yard/garden, growing mealworms (actually beetle larvae), oriental grocery stores... Bob Fenner>

Piranha/Biological Filtration
I read through the Piranha FAQ the other day and found it very informative. I've kept fish since I was very young and have had good "luck" with them. . . I say luck because I've never done anything special- they've pretty much just stayed alive for me w/ minimal maintenance, supervision, cleaning, feeding, or much care at all, really. . .
<Good>
Well, I currently have a 9" Oscar in a 50Gal, three 3.5" Jewel Cichlids in a 30Gal, and some small tetras in a 5 gal. . . I'm also cycling (for the first time, LOL!) a tank to be ready for some baby Red Belly Piranha. Their beginner tank is 30 gal for five 1.5" Fish and I plan to move them up to a 50, and eventually 100, gallon tank. I've had a Red Belly before (10", solitary fish, died at 10 years old) and am quite familiar with the mannerisms of the fish- at least as a single fish. . . and I'm really looking forward to my new crew! I would like very much to care better for these fish so that they're healthy and grow large.
<Sounds good>
I've been reading up on balancing the fish's diet, etc. . . and think I'm ready to handle that aspect- my old Piranha ate live feeders only and would go through about 6 large feeders in a week period and fast for three weeks. . . poor fish! I do have some question as to the filtration of the aquarium, however.
Since I am new to the concept of a biological filter- although have obviously always had usually more than one per aquarium- I just wanted to verify that I have the right ideas in mind. I'm pretty sure that I've only had luck w/ water quality simply because of my little maintenance or feeding in combination w/ enough space for the fish involved- I never killed off the bacteria or created poor water conditions w/ too much waste (??. . .that's the only explanation I have. . .)
<A likely one>
SO, to keep my new fish healthy, I have set up in my 30 gal 2 biological filters, each designed for a 20 gallon tank. That's all I have available now and I figured that I can alternate and clean one per month in siphoned tank water. . .will this work?
<Should>
Do they have to be cleaned, it's just to get debris/waste out, right?
<For the most part, yes>
Thanks for your help. . .I'm very exited about my new additions!
Aja Harris
<I encourage you to institute regular water change-outs, gravel-vacuuming... with pre-mixed, stored water... and to add some circulation to the system. Bob Fenner>

Re: Piranha/Biological Filtration
Thanks. I do have the tank set up w/ some places to hide, as well as an airstone and a powerhead for circulation and extra oxygen in the water. I added the fish last night- they seem to be doing well so far!
<Ah, good>
Question about vacuuming the gravel - am I supposed to press the vacuum down into the gravel, or just skim the surface of it? I've always pressed it into the gravel in the past, but am wondering now if that will negatively effect the biological system (??)
<Vacuum half at a time... see WWM re...>
Also, what are some tips on softening the water and stabilizing the Ph?
<Also posted on... WWM>
I know they're related. . . I have very hard water (live in Baltimore, MD) and I know that's bad for the fish- it seems to be constantly lowering my Ph as well. I know Piranha like a lower Ph, but I can't keep it above 6.0 for long at all. . .
<Actually below...>
AND it seems that no matter what I do all of my tanks end up w/the same water chemistry in the end- my Cichlid tanks, my small tetra tank, and now my Piranha tank as well. Hard water (400+), low alkalinity (0), and low Ph (6.0) My ammonia and nitrate levels are at (0) in all as well- at least that's good. . .
Thanks!
Aja
<I'd be investigating and investing in an R.O. device... Bob Fenner> 

Piranhas filtration
Hi, I have a 100 gallon tank and 5 red bellied piranhas. I was wondering if a lot plants would give enough oxygen to the piranhas with no top water disturbances. and are there any filters you recommend for the 5 piranhas and 100 gallon tank ( internal and isn't noisy). See I have the piranhas in my room and I cant sleep with loud water disturbances or noisy filters. I wanted to put a lot of plants and an submerged filter. I was wondering the best filter I could use that can be completely submerged and no water disturbances. or are there any other oxygenizing methods I could use?
<For this size system, this number of fishes, likely wastes... I would use two good-sized (large) power hang-on the back filters... and if possible, direct their discharges (some you can, some you can't) to move the water in the tank in a large "swirl" or vortex... if not direct-able, I would add a couple of large powerheads (I like the Tunzes, but they're expensive... maybe Hagen or Aquarium Systems lines) in both upper, back corners to generate the same sort of water flow... Only clean one of the filters per week to preserve biological filtration... along with water changes... Bob Fenner>

I'm getting some Red belly piranha's  07/02/05
Is it ok if I only get two or should I get more? And is it cheaper to buy everything together or separately? If you can please help me.
              Thank you for your time,
                     Jodi Sue Strong
<More are better, social animals... if you have the room, mechanicals for them (filtration, aeration, circulation)... a good twenty to thirty gallons minimum per individual. Likely it is less expensive to acquire more gear, livestock at once. Bob Fenner>

Piranha help... basic aquariums 101  - 01/12/2006
Hi there
   <Greetings>
  I recently purchased a new 65 gallon tank, set it up for a few days and finally purchased 4 new red belly piranha's.
<Uhh... hold on a minuto... was this system cycled?>
The first day they were fairly active but as the days went on the slowed down and would only float at the top and have no power.
<Classic... "new tank syndrome"...>
During this time they also developed white spots over their eyes. Finally, all 4 eventually died and I replaced them with 3 more.
<Uhh, another moment please... peek-a-boo>
This time all 3 looked to be fine until about 4 days into getting them when 2 died and one is now very slow again and developing the white eye thing. Can you please help me figure out what is wrong and what I should do before buying more piranha's?
  Thank you
  Colin
<Time to go back.... way back... Please start reading here: http://www.wetwebmedia.com/FWSubWebIndex/fwset-up.htm
then on to the linked files (in blue, generally above...) where you lead yourself. Bob Fenner>

FW chem., too lazy to search WWM... pH Trouble    3/29/06
Hi! I have a Red-Bellied Piranha in a 20-gallon aquarium.
<How large is this animal?>
Recently I have had trouble with the PH. It has been at extremely high levels  (like 7.6). I've tried to lower it by using Ph Down, but even after using it 3 times the PH has stayed the same. Any other suggestions on lowering PH? Thanks!
<... such changes need to occur outside the system... gradually, with water changes. Please see here:
http://wetwebmedia.com/FWSubWebIndex/fwph,alk.htm
and the linked files above........ Bob Fenner>

Keeping Piranhas with Tropical Fish   10/5/06
Hey,
<Hi Ryan, Pufferpunk here>
I have a 55 gallon tank. Currently there are 2 small tetras, feeders and a 4 to 5 in Oscar. I am about to put in six 2in piranhas (red-bellies).
<HUH?  Are you joking?  Those piranhas, at any size, will eat the tetras (eventually eaten by the Oscar) & bite chunks out of your Oscar!  That tank is just large enough for the Oscar, when it grows.  Don't add any more fish to his tank.  Even a 55g is a bit tight for a full-grown Oscar.>
Should I be worried that the larger Oscar might kill the small piranhas?  Likewise, will the piranhas to better if introduced to the tank with no other fish present?
<The piranhas should be introduced into a separate tank.  The Oscar will soon eat the tetras or any other fish it can fit into it's HUGE mouth.  I do not recommend feeding your Oscar feeders & find homes, or return the ones in his tank.  They carry disease.  Get him earring pieces of fish, scallops (or whatever you can find in the fish dept of your grocery store that he likes), krill & Cichlid pellets.  ~PP>
Thanks, Ryan