I recently acquired 18 healthy specimens of the pygocentrus nattereri (red belly piranha) ranging in size from 4-inches to around 8-inches. In these pix, I had all of them housed in my 65g tank as I had not yet cycled the 125g tank I planned on keeping them in yet. I was appalled at the fact that the individual I got them from had kept all 18 of them together in a filthy 45g tank and admitted not having fed them in more than a week.
Anyhow, I also have 3 3-4-inch specimens in another 55g tank as well and have the 125g tank, a 75g tank and 3 more 55g tanks almost ready to go. I will post more pix as I get everything set up!
Sorry about the quality of the pix but they were taken with my phone. I'll also try to post some video shortly as well!