A water storage tank is a solid storage system with a unique combination of quality and mechanical strength. The very high tensile strength makes these steel water tanks robust and very suitable for storage applications. The water tanks are modular and based on curved corrugated steel plates. These plates are galvanized at both sides. In combination with different covers and roof systems, the water tank can be composed into a fully closed water storage system for the horticulture, especially for irrigation and aquaponics. The tanks can be additionally protected by a Plastisol coating layer. That ensures that they remain stainless.