We have a lot of members here that I think pretty fairly represent the piranha holding populous in 1st world countries. Why not have some kind of census. As long as people are honest you get a pretty good idea about rarity and what not.
I like the idea....Im just not sure how it would work because of how rapidly people seem to buy/sell these fish. If there was a program we could use where people would be able to modify what they have...and it would remove their old numbers from the total and put in the new ones....that would be cool.....I just dont know if there is one.