Hello Reef2Reefers! We wanted to spend a few minutes talking today about the wonderful world of T5 bulb changes. It may come as a surprise, but the question pf "how often do I need to change my bulbs" is the most popular question we get. Admittedly, people might be a little afraid to ask this question because they feel it is too simple and should know! I can tell you that by not asking and not knowing, and guessing when to make a bulb change, could be the mistake that hurts the health and life of your corals. Factors that Affect Bulb Life Photo Period: This is the length of time a bulb is running each day. (For example, a bulb run for 12 hours per day should be replaced more often than a bulb run for 8 hours per day.) Heat: Hotter installations typically mean shorter bulb life. We always recommend the use of fans inside a canopy or other enclosure. Also, make sure that hot air can ventilate/escape somewhere. (Remember, hot air rises. So, some slots in the top of a canopy, or removing the top completely can help a lot.) Also, choosing a fixture with an active cooling system is generally a good idea. Be sure bulbs are installed in the proper orientation in your fixture. The end with the label should receive the most cooling. Ballast: Programmed-start ballast typically provide better bulb life than instant-start ballasts, as they are easier on the bulb during start-up. We generally do not recommend over-driving any T5 bulb, as it will shorten bulb life by about 50% and produce more heat. Also, over a 6 month period, the bulb will generally produce less total light than a normally-driven bulb. When to Replace Coral Health: If your corals are not opening up as much or are growing a lot slower than before, it can be a good indication that your bulbs need to be changed.* Soft corals that are reaching towards the light may also indicate the output has diminished and the coral is no longer receiving the amount of light it prefers. Tank Health: In a mature tank with stable water parameters, an algae and/or cyanobacteria bloom can be a good indication that the bulbs are deteriorating and need to be changed. Time: With typical daily photo periods of 8-12 hours T5 bulbs carry the average life-span is 9-12 months. If it’s been more than 12 months since your last bulb change, it’s probably time for a change. How To Replace New bulbs typically produce twice as much PAR (output) as old bulbs. To avoid shock to your corals it is always best to spread out a bulb change over a period of several weeks (Reef tank golden rule: nothing good happens fast). Change out just 1 or 2 bulbs per week. Doing so will allow your corals to more easily acclimate to the new, brighter bulbs. Brand new lamps have a burn in period of 50 hours. During this time they should not be dimmed; if using a dimmable fixture. They may also illuminate inconsistently or flicker during this period. Don't worry this is perfectly Normal. Keep your bulbs in perfect shape, beautiful and happy corals will come easier! Tell us a little bit about how often you change your T5 bulbs. Are you running a strict 9 month change schedule or do you sometimes run a little longer then the 12 months? We would love to hear about any schedules or tricks for your bulb changes so post in the comments below. * Please note, many types of corals may not open up as much as before immediately after replacing your bulbs. http://www.atinorthamerica.com Visit our YouTube channel to view instructional how-to videos about ATI products.