i don't ship when it's that cold.
I get fish store boxes, when they are done with them, for free. When I ship, I ship a lot. Otherwise I use smaller boxes that I collect from the lab at work.
There is a spray insulation, called Great Stuff, or something like that. I wonder if you could seal up the homemade styro boxes with that stuff. Get the low expanding kind if you want to try it.
Pharmacies will sometimes have boxes they need to get rid of, but lately they are recycling them. I use Quarter size 2 mil square bottom bags from Quality Marine, out of Florida. I've ordered from them twice in the 10 years I 've been in business, not that I sell that many fish, but that they give you a lot of bags. These bags have no pockets that fish can nose into and suffocate.( Many square bottom bags do have pockets, and that's a really bad thing.) One sixth size is a good size as well. For the quarter bags, I can put 9 really large clownfish, or 18 small ones, with good results.
I twist and use double and quadrouple rubber bands. I always double bag and then use a big bag to line the whole box. I own a castration device, but found it impractical.
<message edited by KathyL on Saturday, December 21, 2013 10:49 PM>
check out Kathy's Clowns, llc website:
http://kathysclowns.com Captive bred clownfish and more
(Wholesale to the trade.)