The Wavereef In Sump UV reactor is a simple way to add UV to the aquarium. Simply sit the reactor in the sump area and allow the feed pump to pull water through the reaction chamber, the smart T5 UV bulb will adjust to water temperatures to ensure maximum life of the bulb. Small model will hang on the side of the sump. Small (Hang On) Bulb life approx 10000 hrs 18w UV bulb For aquariums of up to 220L Dimensions: 46.7cm H x 9cm L x 9cm W Medium Fitted with an adjustable flow gate valve Bulb life approx 10000 hrs 27w UV bulb For aquariums of up to 500L Dimensions: 61.1cm H x 12.1cm L x 11.4cm W Large Fitted with an adjustable flow gate valve Bulb life approx 10000 hrs 40w UV bulb For aquariums of upto 1500L Dimensions: 61.1 cm H x 14.1cm L x 13.4cm W