T8's lower light output over time with no use? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 11-17-2009, 06:55 PM Thread Starter
T8's lower light output over time with no use?

Do T8 bulbs loose light output over time even if they are not in use?

I dug out some old T8's recently and they look awfully dim, though they haven't been used even once IIRC.
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post #2 of 3 Old 11-18-2009, 11:47 AM
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I've never read of this happening. All fluorescent tubes decrease their intensity as they burn, because the phosphors inside the tube are literally burning. But without being on,...

Perhaps you used the tubes in the past longer than you remember. The intensity diminishes considerably after only three months of daily use, and after that it's a steady decline in intensity. Some authors suggest replacing tubes every six months, but as this is expensive, they recommend 12 months but alternating so one tube is replaced every six months to maintain a better intensity long-term.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #3 of 3 Old 11-18-2009, 04:57 PM
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Not all T-8 tubes are the same. Some are 32watts and others are 40. If the bulb has a Lumens rating that may help. Most T-8's these days are rated around 2700-3000 for 32 watts and 3400-3600 for 40 watts. But I agree with Byron. They only wear out with use.
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