Makes fighting green water easier. UV radiation is effective in controlling bacteria, yeast, molds, and other pathogens, in turn controlling algae growth. Water flows in direct contact with the UV lamp, intensifying its function of fighting green water. In addition, it can be hidden behind ornaments in your aquarium, cutting back on tubing around your tank. 9W Model (UV9WPL) Treats fresh and salt water aquariums up to 53 U.S. gallons (200 L). Completely submersible and sealed to ensure no water leakage. Has a 12V internal UV sterilizer with power head. Uses a 9W sterilization lamp (replacement lamp sold separately). Built-in LED indication for UV sterilizer replacement (replace lamp tube when LED is off). Child Safe 12V low voltage design. Filtration pump (200 L/hour) and sponge included. Zigzag flow designs for maximum sterilizing time. Requires no tubing, has one plug to work both the UV sterilizer and filtration. Assembled unit measures 7 1/2"L x 1 7/8"W x 4"D.