When a fluorescent tube is lit, it is emitting rays of light, from all points around its circumference. When the tube in question is over an aquarium, any rays emitted from the top half of the tube are directed away from the water, and are wasted. By using a suitable reflector behind the tube, it is possible to obtain the maximum efficiency from the tube, because this otherwise lost light energy is re-directed to where it is required - into the aquarium. All Arcadia reflectors are manufactured from sturdy corrosion resistant aluminium, and the design is such that they can easily be mounted to the aquarium hood by inserting the lamp clips through slots in the reflector. The reflector can then be angled to direct the light. One reflector per pack, also comes with stainless steel clips