There is provided a control device (100) for a water tank for watering of animals, and a corresponding water tank, which has few parts within the reach of the animals, is sturdy, and is reliable in spite of litter in the water and in harsh outdoor conditions. A water level indicator (110) is arranged for providing an indication if a current water level in the water tank is below a predetermined level LP. The control device is arranged for actuating a supply means (120) for supplying water (20) into the water tank based on the indication. The water level indicator comprises a temperature sensitive element (111) arranged at the predetermined level. The indication is based on the temperature sensitive element detecting a temperature difference caused by a difference in heat transfer as a current water level is below or reaches the predetermined level.
