Water content of dry feed ingredients and formula feed is generally below 13 %. Therefore, when storing feed in a chilly environment at relative humidity of 70 % or so, molds are unlikely to generate. However, for a long-time storage or in the rainy or summer seasons, feed absorbs moisture, and water content in feed may exceed 15 %, depending on the storage condition. As water content in feed increases, molds in the feed activate and grow proliferously, causing loss of nutrients and deterioration of taste. Some mold species produce toxic substances such as aflatoxin and they will possibly cause adverse effects to Aquatic and Animal Feeds. Molds are more likely to generate at higher temperatures and on pellets and smaller-particle feed. The substance which has a function to suppress generation of molds is called mold inhibitor.