The AA/Green Killing Machine Internal UV Sterilizer Spare Bulb makes fighting green water easier. This is because 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 wter. In addition, it can be hidden behind ornaments in yhour aquarium, cutting back on tubing around your tank. Features: Completely submersible and sealed to ensure no water leakage 12V inernal UV sterilizer with pwer head Uses a 9W sterilization lamp (replacement lamp sold separately) Built-in LED indication for UV Sterilizer Child safe 12V low voltage design Filtration pump (200 L/hour) and sponge included Zigzag low designs for maximum sterilizing time Requires no tubing, has one plug to work both he UV sterilizer and filtration Includes: 1 Green Killing Machine Internal UV Sterilizer Intended For: Fresh and Saltwater Aquariums up to 53 lb Material: Liquid Dimension: Assembly unit measures 7.5 in L x ⅞ in W x 4 in D Dimension: Available in 9W and 24 W sizes Size: 24W.