As with any food preparation product or food storage container, proper maintenance and cleaning is required to make sure that your Baby Brezza Formula Pro stays clean. In addition to the regular cleaning recommended in the instruction manual, we recommend that care be taken when pouring formula powder into the powder container. After pouring powder into the container, check to make sure that no powder has spilled in the area next to the water tank, and clean any excess powder that has collected on the machine with a damp cloth. Also make sure that all parts of the powder container are completely dry before assembly. Mold should not grow in Formula Pro when its properly cleaned and dried.