TETRA UV REPLACEMENT Quartz Sleeve ( UV1 ) ** Manufacturer recommendation is to service your filter once every year to year and a half ( 12 - 18 months ) Service PLS9 Tetra Greenfree UV1 1800 Brand NEW in the BOX INCLUDES: ONE - TETRA UV REPLACEMENT Quartz Sleeve ( UV1 ) A UV Filter will lose its effectiveness if you do not regularly service the components. This can result in green pond !