A large professional pond filter setup that is ideal for both koi and goldfish ponds. Both bays contain filter foams - first a blue coarse foam then finer yellow foams which catch all but the tiniest debris particles. Included with the PondXpert MultiChamber 18000 is the GreenStop Pro 36w UVC is included which fits snugly onto the back of the filter box. This powerful UVC will prevent green water and should be installed in front of the filter. * Saving based on buying items individually. NOTE: UVC bulb included.