i have used this method before when i bought out a local breeder but at that point i had no interest in breeding. so i had to cull off an entire colony. i took a small bucket of dryice and placed it in a larger bucket. i then added the mice into the larger bucket. i added water but i dont recommend it. the mice get wet and then stick together after you freeze them.
c02(the gas dry ice puts off) is heavier than air so i would get a bucket or even a soup can and drill holes in it and suspend it above a screen that covers a larger bucket holding mice. it should take less than a minute. make sure their is a screen keeping the mice in the bucket the will start to freak out and jump like crazy.
adam jeffery
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" a.k.a. farfrumugen "
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.