bags

What is a good planning factor for bags per box for a standard styro shipping box? The bags in question would be large enough to accomodate 4-6" fish on an airplane (i.e. couldn't be packed too tight). A friend in California is planning on packing a couple of boxes of fish to check as luggage...

Anyone know a good source for fish bags. I am not really interested in buying them from the pet store at the mall for $0.10 a piece. It is fine for a few, but I have bigger plans in mind. My LFS won't even sell them at all.