Good Evening Reefers! Have you ever looked at your tank, and said to yourself, "What is a T5?" A T5 is a glass tube containing argon or krypton, phosphors and a tiny amount of mercury. When electricity is applied to the electrodes on the end an arc is formed across the tube producing UV energy. This UV energy excites the phosphors which in turns causes them to emit visible light. What does T5 mean? Well the T indicates tubular, and the 5 means the lamp is 5/8” in diameter. Another example is a T8 would be 8/8” or 1” in diameter. The type of phosphor determines the color, some examples: Â·Calcium tungstate ----------- blue Â·Strontium chloroapatite ------ blue Â·Barium titanium blue --------- green Â·Zinc sulfate ----------------- green Â·Magnesium fluorogermanate -- red ATI Lamps are designed to run in ambient air temperature at 95 degrees Fahrenheit. Output will drop about 1% ever 2 degree rise in temperature above 100. This is why ATI fixtures are built with a fan, to keep the lamps as cool as possible while operating which increases life span as well as output. Proper orientation of lamp (put the end with the label opposite the vent where the air exits the fixture) allows the heat from the cathode to be distributed down the lamp which warms the middle. Lamp Seasoning is a critical aspect most reefers overlook. Seasoning of the lamp occurs in during the first 50 hours of operation. This seasoning period allows the mercury to evenly distribute throughout the lamp aiding consistent output throughout the whole lamp. Seasoning should be accomplished at full output. Hope that sheds some light :laugh: on what's going on in your fixture! http://www.atinorthamerica.com Visit our YouTube channel to view instructional how-to videos about ATI products.