Methods and systems for treatment of grain for toxins and/or odor utilize a storage container having a grain storage space and an aeration floor that allows air to flow through the aeration floor into the grain storage space. Ozone (mixed with air) is supplied to the grain through the aeration floor under positive pressure, whereby ozone is forced through the aeration floor into a lower portion of the grain storage space. After an initial treatment time, the initial treatment time allowing for the ozone to reduce toxins and/or odor in a lowermost portion of the initial quantity of grain an effective or desired amount, a lowermost portion or a lower treated portion of the grain in the grain storage space is removed, and new grain is added on top of the grain in the grain storage space, all while continuing to supply ozone through the aeration floor under positive pressure.