I have shipped fish using both USPS Flat Rate boxes and Styro boxes i can get for free from a local Free Clinic.These were used to ship insulin and other meds,they are pretty much airtight.I boiled some fish to death this summer using this styro box(yuch). What tips do you have for sending from No.Michigan were it is now cold to say California? I already use Bag Buddys and 40-hour heat-paks.For oxygen i just blow the bags up with my airbrush compressor,anybody ever use canned air/oxygen? Thanks,can we talk?