While the koji mold is growing for 2 days, I take the trays out twice a day in order to mix the grain around. This incorporates air into the mix and redistributes the grain, as some of it may have dried out a little bit too much and some may be too damp. When I put the trays back in, I rotate them – top to bottom, right to left and back to front and vice versa, as the heat cabinet will invariably have warmer and dryer areas. This gives a much more even growth.