Tetras Thrive When Right Temperature Is Provided --- Neon tetras, in their native Amazon habitat, live in a temperature range between 70°F to 81°F. This ensures their optimal comfort and metabolic efficiency. Any temperature below 70°F will cause your tetras to enter a state of minimal activity and they will be stressed and miserable. Make sure they are at their optimal health and performance with this heater. Automatically Reaches The Preset Temperature --- The smart SunGrow heater for freshwater fish has a built-in electronic thermostat to automatically maintain water around 75°F which is ideal for most tropical fish. It saves you from the trouble of constantly keeping a check on the temperature of your tank. It will automatically shut down when it reaches the desired temperature, no manual adjustment is needed. Fully Submersible Water Heater --- This 10-watt aquarium heater supports 1.5 gallons (5 liters) fish tank. Its exterior is designed tougher than glass and the sealed polymer can be submerged into your tank. The heating element is surrounded by thick plastic to ensure the protection of your fish.