housing other fish with piranhas

Question
I have a 55 gallon tank with 2 Red Belly Piranhas at about 7 inches each. I
have a large Penguin filtration system and replace about 20-30 percent of the
water each week.
    What I would like to know is if there is any way I can house other fresh
water fish of comparable size in the same tank as the piranha. Specifically, I
wanted to add one Arowana around 8 to 10 inches in size. I was hopeful that
by adding large objects like logs into the tank, the fish could hide behind
them and claim their own territory, and also by keeping a steady supply of
feeders, that they would be "peaceful" to each other. Is this to much to ask
for? Should I seek a larger Arowana or forget the idea altogether?

Answer
NOOOOOOOOOOOOOOOOOOOOOOOOO!!!!


First off, I am surprised your piranha are still alive. They are schooling fish, they need at least 6 of each other and at least a 125g tank. Without it there will be too much agression. I'm guessing your pirnaha's tails are shredded already, if not then they are simply to sick or stressed to fight.

To house red bellied piranha with large tank mates is unheard of in tanks under 1000 gallons. They are piranha after all. Not only do arowanas need 250g tanks (they do grow you know, regardless of what size you bought them at), but an arro with piranha, even in a 1000g, 2000g, or even 3000g tank would be shred to pieces in weeks.

Do some research BEFORE buying your fish. Your tank is unsuitable for what you have now, if anything you should be thinking of seperating or finding a new home for one of your piranha, tank mates should be the very last thing on your mind.