0.1 to 0.2%. Oregano is a spice that is commonly used in cooking and flavoring by looking at the oregano product directions. In aquaculture, oregano is also used as an additive, and the dosage of oregano in aquaculture feed is 0.1 to 0.2%. The addition of oregano can improve the taste and nutritional value of the feed, but care should be taken not to affect the balanced nutrition of the feed.