Double wall construction for longer life. Uv indicator light. Mounting brackets and connectors included. Uv lamp included. Eliminates single-cell algae and harmful microorganisms for crystal clear water. 3X/9 Watt is for freshwater or saltwater aquariums up to 125 gallons. 6X/18 Watt is for freshwater or saltwater aquariums up to 250 gallons. 12X/36 Watt is for freshwater or saltwater aquariums up to 500 gallons.
