In order to clean the pipes , Kiseru seperates the mouth piece and the front piece from the stem. He then inserts the mouth and the front piece into a type of fish tank where tiny fish swim into one end of the pieces and come out the other. These fish apparently live off tobacco residue and so they eat whatever tobacco is stuck to the walls of the pipe. In other words, they clean it perfectly. The two pieces are then taken out of the tank and fitted perfectly onto a new stem.