The 300w 100w 50w Submersible Aquarium Heater is a high-quality, durable heater that is perfect for keeping your fish tank warm during the winter months. The heater features a blue powder coating that protects against scratches and corrosion, and the quartz glass ensures that the electricity stays within the heater itself. The heater also has a free thermometer that allows you to keep track of the temperature in your tank.