[bettababy]

I will have to side with Blue on this one. His information is accurate.

There are other species of piranah, and yes, some are more aggressive, but to eat a cow you would need many fish. The stomach on a piranah can only hold so much at a time, and there is a lot of waste involved, as was also pointed out.

If you take a dinner plate and hold it up to a 15 gallon tank, or even a 40 gallon tank, you'll get a good idea of how big most species of piranah will get. In the case of wanting up to 6 of them, hold up 6 plates, and common sense would tell you that it won't work. The fish need room to swim and turn around comfortably, which, in a small tank, won't be possible once the get too big. The same problem is true for 55 gallon tanks, they are too narrow, and the fish can't turn around properly once they get larger.
It would be very helpful to know your tank size, either number of gallons or dimensions.

 

[bettababy]

The thing that stunts the growth is a high nitrate level over a period of time. With that said, it also will slowly poison the fish and cause a lot of internal damage if not cleaned up. A healthy fish in good water quality will grow to its full potiential size.
Putting a piranah in a 10 - 15 gallon tank will only accomplish one thing overall... it will kill it!

I have told this story in other threads here on ff, but I will tell it one more time to get the idea across.
A few yrs ago, while still working at the store, a guy came in with a 10 inch jack dempsey. This was the prettiest dempsey I had ever seen, bright colors, etc... but the spine was "kinked" severely. We put the fish into a 40 breeder quarantine tank, and it died within about a wk.
The customer told us how he'd raised it in a 10 gallon tank, doing 100% water changes every day and feeding good foods twice/day. Now, picture a 10 inch dempsey in a 10 gallon tank, and you'll understand why the spine was kinked. By the time the guy brought it to us, it could not swim, nor could it hold istelf upright in the tank, because of the deformities in the spine which were due to lack of space.
The fish was almost the same size as the tank. This was one of the saddest things I've ever seen.

In the case of a piranah, when full grown, it would be too tall for a 10 gallon tank... and the same problem would be an issue as with the dempsey. So, could you raise a piranah in a 10 gallon? NO. Plain and simple... NO. The average life span of a dempsey is about 50+ yrs... the average life span of a piranah is about 40+. The dempsey was about 2 yrs old when it died... what a waste. Piranah tend to grow faster than even the dempseys, so you're talking about maybe an 8 month - 1 yr lifespan for a fish that should live 40+.

How else to say this? JUST DON'T!

 

[bettababy]

pygomania, am I reading your signature correct with 10 gallon containing 3 koi and 2 goldfish? How long have you had them? How long until they go into a bigger tank? That is also something I suggest against.... koi get way too big, as do goldfish, plus they're messy fish.

 

[bettababy]

blueblue48... how big of a tank are you thinking for them? How big are the $65 fish? Usually the price will reflect 2 things specific... the cost of keeping them until they sell and the size of them at the time of sale. The smaller (and younger) fish tend to sell for less because the LFS hasn't invested much into their care... but as they grow (which happens quick), they cost more to care for. For the LFS to actually make any profit, the price then must reflect this.