How Do I Replace T5 Bulbs and How Often Should I Do It?

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 of “How often do I need to change my bulbs?” is one of the most popular questions we receive!

Admittedly, some people might be a little afraid to ask this question because they feel it is too “simple” or self-explanatory. However, it is not as straight-forward as replacing a bulb in your home or office at all… Replacing T5 Bulbs incorrectly can actually be harmful for the health and life of corals in your aquarium. Therefore, it is a very important process to consider!

Factors that Affect Bulb Life

  1. Photo Period: This is the length of time a bulb is running each day. For example, a bulb running for 12 hours per day should be replaced more often than a bulb that operates 8 hours per day.
  2. Heat/Cooling: Generally, the hotter the installation, the shorter the bulb life.
  3. Ballast: Programmed-start ballast designed specifically for high-output fluorescent bulbs typically provide better bulb life than instant-start ballasts and other types of fluorescent ballasts. This is because programmed start ballasts are easier on high-out T5 bulbs during start-up. They gently ramp up voltage to the bulb until it turns on, while in contrast an instant-start ballasts turns on at full power and then ramps down to the correct operating voltage.

How to Improve Bulb Output and Life

  1. Reduce Photo Period: Simply reducing the amount of time the bulbs are on each day can significantly improve bulb life. Even a relatively small reduction of 1 hour per day can extend bulb life by up to 1 month.
  2. Use a Fixture With Built-in Fans: Choosing a light fixture with a built-in active cooling system, like the ATI SunPower or ATI Dimmable SunPower, will usually increase the output of your T5 bulbs and improve their lifespan. You’ll just need to be certain that the bulbs are installed in the proper orientation in your fixture. The labeled end of the bulb should receive the most cooling.
  3. Cool the Bulbs “Hot Spot”: The hottest part of a T5 bulb is the labeled end of the bulb. Gently cooling this area can improve bulb life.
  4. Add Fans / Ventilation to a Canopy of Other Enclosure: We always recommend the use of fans inside a canopy or other enclosure. Also, you’ll want to ensure that hot air can ventilate/escape somewhere. Remember, hot air rises, so adding some slots or cut-outs in the top of a canopy, or even removing the top entirely, can help a lot.
  5. Do Not Overdrive the Bulbs: We do not recommend over-driving any T5 bulb. This is because it will shorten bulb life by about 50% and produce significantly more heat. This will not provide more light over the bulb’s lifespan. In fact, over a 6-month period, the bulb will generally produce less total light than a normally driven bulb.

When to Replace T5 Bulbs

  1. Coral Health: If your corals are not opening up as much or are growing a lot slower than before, these can be indications that your bulbs may need to be changed.* Soft corals that are reaching towards the light may also indicate diminished output. In that case, the coral is no longer receiving the ideal amount of light it requires.
  2. Tank Health: In a mature tank with stable water parameters, an algae and/or cyanobacteria bloom can also be an indication that the bulb’s light spectrums are deteriorating and need replacement (assuming nutrients and other water conditions remain unchanged).
  3. 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.

* Please note, many types of corals may not open up as much as before immediately after replacing your bulbs.

How To Change Your T5 Bulbs

  1. Do It in Stages: 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).
  2. Change Out 1 or 2 T5 bulbs per week: By doing this, you will allow your corals to more easily acclimate to the new, brighter bulbs.
  3. Burn Them In: If you plan to dim your bulbs, please make sure you run any new lamps at full power (100%) for the first 50 hours of use before dimming.**

** It is perfectly normal for bulbs to illuminate inconsistently or flicker during the first 50 hours or so of use.

If you keep your bulbs in good shape and replace them on time, 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 than the 12 months? We would love to hear about any schedules or tricks for your bulb changes, so please feel free to share your experience in the comments below!

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