what you should do is...try not to put too many shrimps in a bag. get the person who sold them to you to use a bigger bag, fill with actived carbon and ammonia chips. shrimps usually would foul the water faster than fishes,thats why carbon / ammonia chips are needed. place the bag into a foam box, with a piece of dry ice wrapped with newspaper, better if you can get saw dust. seal the box to keep the inside of the box cool. do not use tranquilizers...for it would kill the shrimps outright.
if your fight is 8 hours, then the total time should be over 18 hours, taken into account the time they were pack, journey to the airport, the customs, the wait, the flight, landing , clearing, and the journey back to your home.
the bad news is...the longest period i have tried using this method is 15 hours, well, maybe you could get lucky..ha

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