Piranha bite when stressed and when they are inticed with some type of food. There sharp little daggers move about a zillion miles an hour when stressed. No wonder you got bit lol. You probably stressed it out a little to much and you just happened to catch the buisness end. Sorry man I know how bad that hurts. I got bit by my old Beani and he has some massive teeth. Bit me right in the wrist almost at the vein. Hurts like a MUTHA^$$&^%^. I bet you screamed a couple words lol.