A dead prawn is used to establish the cycle that keeps ammonia and other bad stuff processed. The first few sand shrimp may survive if the cycling process is done right. It is a complicated process if you want to it "right" but it doesn't take much to make it work. Just have to keep something in there to keep the tank ready for more shrimp.

I have a full article on it if anyone wants it.
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Taking my fishing poles with me to a body of water that has fish in it is not an excuse to enjoy the scenery.