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Fluorescent Lamps

A friend was getting inconsistent information about his compact
fluorescent lights.  I had heard that they maintain nearly the same
lumen output for their entire lifetime, and my friend heard that their
spectrum degrades.  I decided to ask aquatic plant enthusiast and
lighting consultant David Lass what happens to the spectrum and lumen
output of compact fluorescent bulbs as they age?  David, who spoke at
AGA 2000 in Chattanooga, had this to say (bear in mind that David uses
the term "lamp" to refer to the removeable, self-contained system that
converts electricity into heat and light - sometimes called a "bulb"):

> From: David Lass
> Sent: Thursday, December 20, 2001 3:36 PM
> To: Karen Randall; Michael Rubin
> Subject: Re: Looking for David Lass

> In answer to the question (and I just spent today at Sylvania, so I
checked this out with them) The deal is that with any lamps that use the
new triphosphor technology, which is T8's, T5's and compact fluorescents
and power compacts, the lamp loses 10% of its lumen output in the first
1000 hours of burning. For the rest of its life the lamp maintains
approximately 90% of its initial lumen output. There is no decay or
change of the spectral output of the lamp until they are at the end of
their life.

> Typical life for compact fluorescents and power compacts is around
10,000 hours, for T8's it is 20,000. To me this means that you can run
T8's and T5's for 4 years plus,
and compact flos and power compacts for 2 years plus. Folks trying to
sell HO and VHO lamps don't like this, since their lamps have
tremendously steep degradation curves, and they do need to be replaced
every year or so.

> I spent a long time today looking at these new T5 lamps. They are
straight lamps, and I think they are 1 meter long. Use a special
electronic ballast, but 1 lamp is equal almost to the output of 2 T8's.
Because they are thinner (5/8" in diameter) they are even more of a
point source light than T8's. I may try some, although I only have 1
tank that I haven't converted to the AH Supply light kits.