Zapp Pure UV Sterilizersare commercial quality, high performance UV sterilizers designed for Koi ponds up to 40,000 gallons. This exciting new UV was designed to work with today's low amperage pumps and high flow filters, such as the AlphaONE. Sporting an impressive 4" vessel with 2" inlets/outlets means no flow restrictions. These units are truly high performance/high intensity units utilizing over 70,000 microwatts of killing power. Few UV's can make this claim. These units won't nickel and dime you to death. Replace only one lamp instead of several. This could save you big money! Changing a lamp or ballast on these is so simple even an adult can do it. It's not as complicated as programming your VCR. Remove the top cover, unplug the single 4 prong connector, slide out the lamp and insert the new one and you're done. Removing the quartz tube is just as easy.