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All the sites that sell CF's and Metal Halides say that they need to be replaced every year (if not sooner). Could someone explain how they lose their effectiveness and why they need to be replaced? Obviously they will continue to provide light for much longer than that.

Standard flourescents and incandescents have a "life" of many many years so what is the difference?
 
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They do continue produce plenty of light, but the heat causes them to loose their spectrum faster. Standard fluorescents don't burn as hot. I knew of a guy who would rotate his bulbs from his reef tank to his freswater tank then to his garage to light his shop. Talk about getting every pennies' worth.
 

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Color shift. They recommend replacing them because they change color out of the spectrum they were initially designed for, rendering them useless for the intended use. I replace the VHO bulbs on my reef tank every 2 years as an electronic ballast is much easier on bulbs than a magnetic one. MH is very noticable when they have reached the end of their intended life. Like Jared said, the bulbs still work fine, they are just the wrong color.

Paul
 
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$1,195? That sucker was $1,950! Forget the lights, that would buy ALOT of frogs 8)
 

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That's great! There's a free flashlight for every 10 of those!


rmelancon Posted: Thu Nov 11, 2004 1:11 am Post subject:

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You're right, I read it wrong it is $1,950. In that case make it an even 10.
bluetip
 
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Spectrum is just a fraction of the reason.

The biggest reason is the dropoff of intensity (PAR) being emmitted by the bulb. Flourescents (NO, VHO, PC) tend to lose the vast amount of their intensity after about 4 months of use...and even an electric ballast won't help all that much (hope you aren't keep corals under those 2 year old bulbs, Paul). Most people who are serious coral keepers generally switch their VHOs and PCs out every 6-8 months or so, just to try and get some extra money's worth. Granted, they will still illuminate and "appear" bright, but the human eye is a terrible measuring tool for intensity of light. And, the spectrum does tend to shift as well.

As for halides, their PAR life is a decent amount longer than flourescents and their color spectrum doesn't shift nearly as soon, either, which is why most reefkeepers switch them out every 12-18 months or so.

However, for growing plants in a viv, you don't really need to worry as much about any of this because plants aren't nearly as picky in regards to spectrum and PAR in photosynthesizing.
 
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