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When to replace a bulb?


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When is it time to replace a bulb(s)?


I have an 18watt PC on my 2.5 AGA--Pico that I've had running for a little over two-years. Everything is growing great and I haven't seen signs of fading or discoloration in the corals. I've grown accustomed to the lighting that I can't tell (with my human eye) if the bulb has faded.


I've been using the "if it ain't broke--don't fix it" method. Everything looks great otherwise. Any thoughts???


Thanks. :D

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I've been wondering about this myself.


I have heard a lot of things like:


- "You need to replace your lamps every 6 to 8 months becuase the spectrum shifts/degrades."

- "... because the intensity drops off."


But I haven't seen a lot of empirical evidence to back up these claims. In fact, I investigated spectral differences between some new & 8+ month old normal output fluorescents that I had laying around. Not much of a difference as you can see from the spectrographs below. You can find more details about the lamps and the instrument I used on my 20L thread.



New (top) & old (bottom) 15W GE "Sunlight" lamps.







New (top) & old (bottom) 15W GE "Plant & Aquarium" lamps.




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Scott Riemer

I've always heard that PC bulbs change spectrum 9-12 months down the road. Sometimes this shift can cause nuisance algae blooms or affect your corals.


The cost of an 18 watt bulb isn't that much. But, if you wanted to, you COULD buy a replacement, put it in, and see what difference it makes. If you think it's no big deal, you could switch back and then you'll have a replacement for when you need it.


Edit: Mr. Fosi beat me to it.

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Mr. Fosi & Scott--thanks for the input! :D I think I'll buy a replacement bulb and see if there's a noticeable change. If not, I'll have a back-up for a rainy day.


Thanks again for the info!!! :D

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