i put my teeth through my knee and it didnt hurt, i hit a rock snowboarding at like 25-30 mph, and did not feel pain(haha, i didnt feel anything, especially no air in my lungs) so yeah, the guy who talked about times of great stress causing pain receptors to be blocked is correct(there is also lots of documentation). Personally, i don't feel its neccessarly, or very humane to feed live mice to piranha. To the notion it is natural, that is very un-true. If you look at a piranha in the wild, very few ever taste a mouse or other live mammal. I have been reading a lot about piranha lately, they are better scavangers than hunters, and when they do hunt, its fish. If these animals just waited for mice to fall in the water, there wouldnt be very many in existance. Secondly, i would rather feed a fillet of fish, which in the wild makes up more of their diet and is lacking fur, organs, etc. and is soley meat(and occassionaly scales). I do however, seeing myself feeding a dead mouse or other animal to them, because i don't have to watch it suffer. Anyway, thats my two cents.