I dont want to sound critical but I have a 1850g acylic tank and I would not even cosider that big enough, sure you could give it to the zoo, but they are already over crowed with red tails and other gaint fish that stupid lfs's sell to people who haven't got a hope of providing a sutible tank for them. How often do you see people put dogs on a chain in a 8' by 8' yard for all of their lives, when you do hear of it, it is usually b/c of crulty to animals. I am not trying to go on any crusade or anything, I just believe buying a fish without the intent to see it through to the end of its natural life is wrong, and most fish given an adequate tank will live longer than in the wild. So why is it that pirarucu's are so hard to keep at 5' or bigger, its b/c the tanks are way too small.