Items you will need
Polystyrene insulation material
How to Ship Live Fish. Tropical fish hobbyists sell and trade their favorite colorful fish all the time. Unfortunately, not all their customers are in the same neighborhood--or even in the same state. This necessitates the shipping of live tropical fish via the U.S. Postal Service. While it may sound precarious and even harmful to the fish, with proper packing procedures, the fish arrive at their destination safe and healthy.
Refrain from feeding your fish 2 days before you bag them for live shipping. This prevents them from soiling the shipping bag while they're in transit.
Place the fish in 1.5 to 2 milliliter plastic bags. The longer the bags the better. Put one fish in each bag, except for small fish like killifish. Label each bag with an adhesive tag.
Fill the bag with the minimum amount of water necessary. Each bag should be no more than 1/3 full of water. Pump the bag with regular air or oxygen, then twist and tie it closed. You can use a rubber band to secure the tie.
Label your box inside and out and ship immediately after packing. Ask the postal clerk when it will be delivered.
Call your customer and let them know when the live fish will arrive so they can make arrangements to receive and open the shipment immediately.
Insulate your shipping box with polystyrene thermal insulation and packing peanuts. Put Styrofoam shelves between each bag. Ship overnight or express mail in cold or inclement weather to prevent harm to the fish.
Never breathe into the bag to supply it with air to ship the fish. This will kill the fish.