A Fishy Story
As Moses and the children of Israel were crossing the Red Sea, the children of Israel began to complain to Moses of how thirsty they were after walking so far. Unfortunately, they were not able to drink from the walls of water on either side of them, as they were made up of salt-water.
Then, a fish from that wall of water told Moses that he and his family heard the complaints of the people, but that they through their own gills could remove the salt from the water and force it out of their mouths like a fresh water fountain for the Israelites to drink from as they walked by.
Moses accepted this kindly fish's offer. But before the fish and his family began to help, they told Moses they had a demand. They and their descendants had to be always present at the seder meal that would be established to commemorate the Exodus, since they had a part in the story. When Moses agreed to this, he gave them their name which remains how they are known to this very day, for he said to them, "Go Filter Fish!"