1. USPS. ie, The post office.What postal service do you use?
Do you require overnight, or let customer decide?
Do you use pure okygen to ship fish, or regular air?
How much does overnight shipping cost for your postal service?
Do you know what service is cheapest?
2. Depends on the fish, but with hardy shrimp, livebearers, and snails, priority is usually fine.
3. Overnight is usually a minimum of $45, and sometimes as much as $70-$80. Priority, you can use the 'prepaid' boxes that use a flat rate- Most packages will be $11, and only the very largest shipments will me &$14.50. Snails and some plants can easily fit in the $5.50 box
I don't use oxygen, but I do use 'Kordon Breather Bags', which allow O2 exchange through the plastic. I also use 'Bag Buddies'- A small tablet that you add to the water. It adds Oxygen and a fish tranquilizer to keep the fish calm.
Which service is the cheapest? USPS Priority is by far the cheapest, but as far as overnight services go, I don't know.