The OASE HeatUp line of aquarium heaters are designed for marine and freshwater tanks. For optimal heating, utilize the HeatUp 25 to create uniform temperature levels for your aquarium environment. The control system on the heater allows accurate readjustment of the temperature ( /- 6°F) and can be adjusted using the included post calibration tool. The temperature scale can be adjusted between 66°F - 90°F. The HeatUp is perfect for submerged use and includes a thermal shutoff switch for added protection. The heating function is displayed via the activated control light. Temperature levels are monitored and controlled by bi-metal technology for automated heating.