179. Any tanks located below the vessel's center of gravity should be __________.

Tanks located below the vessel's center of gravity should be filled to maximize vessel stability. Filling these tanks eliminates the free surface effect and adds weight low in the ship, both of which enhance stability. Partially filled tanks create a free surface effect that raises the virtual center of gravity and reduces stability, while emptying tanks removes beneficial low weight. This principle aligns with naval architecture practices and stability regulations.