Oh, I forgot: For my sixth birthday, someone gave me a pair of cons in a bowl. They lasted a day.
I saw 5 12" Pacu in a 29 at a LFS.
I think the volume of the tank was 29 gallons, but the volume of fish must have been 25 and the water must have been 4. I walked in, then walked out when I saw that. That and a 1.5' P Bass in a 20L three tanks down. And a foot long around and a foot long RTC in a 20L. They once had a 3 foot long RTC in a 55. I never go there, and my customers complain about that place.