If the crawdads don’t intake any food,and they are given only fresh clean water,they will absolutely purge the sand and poop chute.Ive eaten them both ways,I personally didn’t care as much for the unpurged,but to each his own.Every year I do a few survival bivouacs,I don’t bother purging the crawdads on those trips,but while I’m at home,I make an effort to purge and clean them