Even if the package says `pre-purged’, it is a good idea to purge shellfish one more time to be on the cautious side. For this it is important to mimic the environment the shellfish lived in as closely as is possible. Place Manila（asari) clams in a salt solution (about 2%; at 3% a salty taste many remain) slightly weaker than sea water, and place shijimi (tiny fresh water clams) in fresh water. Place both types of shellfish in a large tub and spread them out, fill to the top with either the salt solution or fresh water. Since a dark place facilitates sand purging, cover the tub with a newspaper and leave for at least 30 to 60 minutes. During the summer months, place in a refrigerator to ensure freshness.