Coralife 08604 Lunar Aqualight High Output T5 Fixture (24inch) spray collar refill Then press ON OFF for 3 Then press ON OFF for 3 seconds (until the number appears on screen) Water is pumped into the sterilizer chamber where ultraviolet light eliminates the unwanted microorganisms resulting in a clean and clear aquarium The directional LEDs can be positioned to add a shimmering moonlight accent over a specific area in your tank or the LEDs can be set to provide a more even distribution of moonlight Lunar Aqualight High Output T5 Fixtures include four high output lamps and directional LED moonlights making these fixtures a great choice for saltwater reef tanks