A person cannot eat fish while on the Daniel Fast. According to the Daniel Fast website, the diet is basically "a vegan diet with even more restrictions."
The diet's official website explains that, when on the Daniel Fast, a person can eat fruits, vegetables and unleavened breads. No meat, yeast, baking powder or soda are allowed. Spices, however, may be used in cooking. Water is the only beverage to be consumed. No herbal teas, fermented or sweetened beverages are permitted. Also when on the Daniel Fast, no chemicals, artificial or processed foods are allowed.
The Daniel Fast is based off a portion of Biblical Scripture and is intended to be a spiritual experience, which encompasses the body, soul and spirit. A spiritual goal is set during the Daniel Fast.