Both for Freshwater and Saltwater aquarium tank use. Unbreakable Carbon fiber plastic housing with stainless steel double insolation, 100% safe for fish and living creature in tank. FULLY SUBMERSIBLE – It can be placed vertically or horizontally.DO NOT place it TILTED. It will not operate if the bottom is higher than the top. Must be FULLY submerged. Temperature range: 68℉-88℉,Top Calibration knob to adjust the temperature