Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
If you can buy several heat packs, then set out the cooler each morning and activate a heat pack, wrapped in a towel. Put the lid on the cooler with the note to the delivery person. PUT PACKAGE IN HERE, thanks :-)
If the shrimp arrive, the cooler will be warm from the heat pack, but the towel will not allow the plastic bag of shrimp to contact the heat pack, so it should gently warm them without getting too hot.
If they do not arrive, you have wasted that heat pack, use a new the next day...