Liz, you give me a lot of hope! In August of 2005, my husband stumbled across the mother of all yard sale finds...a 55 gallon tank chock FULL of big fish...two at least 15" pacu, four large oscars and two 12"+ pleco. Hubby placed the fish into our biggest pots to bring them home. One pacu jumped out of his pot which was sitting on the tailgate of hubby's '63 chevy pickup. After groveling around in the gravel, he was picked up, dusted off and put back in his pot. Once home, the 55 gallon tank, gravel and HOB filters were scoured thoroughly. The tank was filled with our chlorinated water and the fish were put in their now "clean" home. That evening, we got online to figure out which were the pacu and which were the oscars. In our total newbie ignorance, we got another 55 gallon tank from WalMart, filled it up with dechlorinated water and moved the two pacu in. In the following five days, we watched them almost die from the ammonia buildup and horrendous bacterial bloom that occurred. To save their lives, we had to put them back in the original overcrowded 55 g tank. In the last year and a half, we've come a long way from the ignorant newbies we started out as.
Next week, will mark the one year anniversary for our pacu (now about 20"), two oscars and the plecos being in their 300 gallon tank. We lost one oscar to HITH (not surprising as the nitrates were through the roof most of their lives) Freddy, the runt oscar lives by himself in the old 55 gallon tank. We have very innovative plumbing on the big tank which makes tank maintenance very easy. The water parameters have been excellent for the last year (except after a long power outage).
As I said, you give us hope. There is so much gloom and doom predictions on the potential size of pacu, we don't know what the future holds for us. We figured that we have about three years before we'd know if we have to go bigger. We really love our big fellows.
Here's a poor pic taken with a very slow digital camera: