Why are many metals unsuitable for seawater aquarium tanks?

Many metals are unsuitable for use in seawater aquarium tanks primarily because seawater is highly corrosive. The high concentration of dissolved salts, such as sodium chloride, in seawater increases the water's electrical conductivity, which accelerates the degradation of many metallic materials.12

When metals corrode in an aquarium, they can release toxic substances into the water, which poses a significant risk to the health of aquatic animals. While some metals like stainless steel are sometimes used due to their lower toxicity and are often found to be satisfactory in certain applications, nonmetallic materials—such as glass, plastics, and fibre glass—are generally preferred for the construction of seawater systems to ensure the safety of the inhabitants.1