A water level sensor is already included with the GreenBox. The water level sensor measures the filling level of the water in the GreenBox irrigation tank. It sends the read data to the GreenBox app, which informs you about the water level of your GreenBox and lets you know when you need to rewater. Information on filling quantity: When starting a new growth cycle, we recommend filling with 1.5 liters of water. If the plants have already developed more root systems, the water tank can be filled to the maximum — with approx. 2.3 liters of water. In both cases, the plants are cared for an average of 14 days. Water requirements can naturally increase at high temperatures. Free shipping within Germany from an order value of €30.