The Aqua One Tropical T8 fluorescent tubes are specifially designed to provide the light plants need to photosynthesise. Converting carbon dioxide to oxygen within aquarium water is one of the key ben efits of keeping live aquatic plants and a healthy aquarium. This lighting is suitable for tropical, coldwater or plant tanks. 12in = 30.48cm 24in = 60.96cm 30in = 76.2cm 36in = 91.44cm 48in = 121.92cm