A few months ago some 10 year old kid caught a piranha in the Susquehanna river near my home. Apparently someone owned the fish, decided it was too big to keep anymore, knocked out its front teeth and released it into the wild. The average temperature in the river is roughly 50-60 degrees farenheit. So yes, they can survive quite poor conditions. (the kid caught the thing on a worm.)
Vampire tetras in schools?!? :thud: I cant imagine being caught in a feeding frenzy with a bunch of them. Do they have any natural predators?