Jebao 36W Aquarium Koi Fish Pond UV Light Sterilizer Permanent Elimination of Algae Bloomy to Get Rid of Green Water 2G11 base 36w UV lamp pre-installed. All units have 3/4", 1", 1-1/4" and 1-1/2" fittings Complete with 22 ft cord and UL listed sealed transformer. Max flat rate: 4400 GpH For external use only (non-submersible). Install in-line after pond water has passed through a filter for best sterilization effect. For peak performance, the 36w Ultraviolet Bulb should be replaced once every 6-12 months of operation