The temporary bad bacteriological results in some shellfish harvesting areas in Brittany (France) lead us to recommand the use of insubmersible aerate tanks in shellfish plant. The shellfish depuration kinetics are as good as those noted in purification plants using chemically or physically purificated water. The generalisation of this technic to a regional scale corroborates its efficiency and allows us to fix good practice rules. The observance of these rules must lead shellfish-grower to sell, permanently, bacteriologically proper products.