Pond, The radiation from ultraviolet light at 2537 angstroms provided inside the Lifegard Ultraviolet Sterilizer exerts a lethal effect on micro-organisms. UV light alters genetic material within the cells, which interrupts respiration. UV light, when used properly, is extremely beneficial in destroying disease causing pathogens as they pass through the unit. UV sterilization is an effective method of disease control. Four major factors affect the percent kill of free-floating micro- organisms by UV radiation. (l) Size of organisms. (2) Radiation level. (3) The extent to which UV rays penetrate the water and (4) Contact time in which the micro-organism is exposed to the UV radiation. Pure hard quartz material in the bulb dramatically increases UV output compared to other conventional bulbs of equal wattage. Pure quartz material resists solarization and improves the longevity of the bulb. Unique test tube style pure hard quartz sleeve isolates the bulb from water contact preventing thermal shock, broken glass and mercury contamination of the aquarium. This quartz sleeve isolates the bulb to provide an optimal bulb operating temperature of 100 degree F(38 degree C). This higher bulb temperature increases UV output 35% over conventional units without sleeves. Bulb changing is the easiest in the industry. Simply slide the old bulb out and slide the new bulb in. No need to shut down the filter system or turn off the pump. Bulb and ballast connect together with a single 4 pin connector. UV radiation levels can be increased by slowing down the flow rate or increasing the total wattage in the system. UV sterilizers are available from 15 watts up to 240 watts. Tandem mounting will provide proper wattage for any installation requirement. UV sterilization is most effective when used as the final stage of the Lifegard filtration system. It must be understood that micro-organisms reproduce exponentially. The goal is to reduce the micro-organism population to an acceptable level. In certain instances, the wattage may be adequate to eliminate the pathogens flowing through the Sterilizer but the flow rate is too slow to keep up with the total micro-organism population in the aquarium system. In those cases, the flow rate and total wattage must be increased.