Old bulbs

[Roy G. Biv]

Ok, I was doing some thinking today. I am going through some old stuff and ran across some old bulbs. People say that old bulbs have a spectrum shift that causes algae outbreaks. I am wondering if that is that bad.
For instance. I have a 12K halide bulb used for 1 year. If there was a spectrum shift, wouldnt it shift towards 10k or the other way to 14k? Why would this be so bad.
I understand the bulb loses par as it ages, but thats not what this is about. Can anyone explain?

 

[Roy G. Biv]

^^^^^^^^^^^^^^^^^^

 

[Mscott203]

seems like a good question.
Anyone have any further information regarding this?

 

[widmer]

If I understand the situation correctly, the blue aspect wears out sooner than any other. So if you put them in terms relative to each other, then yes my the kelvin rating goes down. But while the blue aspect is decreasing, this doesn't mean that other aspects are increasing, which means the bulb continually moves towards being useless, and then over time it doesn't provide the level of light you need to keep your corals.

 

[46FiatYamaha]

From what I've read the bulbs lose the high end spectrum, or the more blue amount, and also strength with age. Here's a good article
http://reefkeeping.com/issues/2007-04/ac/index.php