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In a message dated 9/22/98 1:01:52 AM Pacific Daylight Time, Aquatic-Plants-
Owner at actwin_com writes:

    I have 240 watts of 4' flourescents (Vitalite) which I am told are
 5000 / 5500 degrees K on a 6' 125 gal plant tank.  I understand this is
 the 'correct' color temperature for optimum plant growth.  I want to add
 some additional lighting in the 2' of the tank that is not fully lit.  I
 have been told that if I get 7100 deg. K power compacts, this is a good
 solution (5500 deg K is not available in the 15" length that I am
 looking for).
 Is 7100 degrees K as good for plants as 5000 / 5500 deg. K.  Does it
 matter?  I have searched the archives and can find no specific answer to
 this question.
IMO (let me re-emphasize) the power compact choice is a good one. Lots of
photons of about the right "temp." (relative to black body radiation) at a
reasonable cost of gear acquistion, replacement and energy consumption... The
bigger question, wavelength, temp., CRI considerations is involved.
Considering other impt. factors such as tank depth, dissolved color, surface
disruption... there are photosynthetic pigments et al. that are more/less
capable/"affected" by differing qualities of "light". Some folks opt for other
definitions of "useful" or "useable" spectra. To some extent (sorry to be so
edgey re) thallophytes (algae mostly) and higher plants can physiologically
"accomodate" to varying/varied qualities and quantities of light/lighting, and
so it might seem that taking into consideration aesthetic desires there would
be one "best" lighting moda functionally (hoboy)... Some folks advocate the
cheapy-cheapiest shop lights and fixtures (reminds me of the algorithm
forwarded and added to many years ago in Science "Mag." for when you might
trade out your old clunker-mobile for new... factoring in gas use, insurance,
rego., indices of instantaneous relative safety, comfort...). Question: will
Cool White (tm) fluorescents "work"? (yep, in many circumstances), Q: Are
Vita-Lites (Dura Corp.) (tm) "better"? (yep, in looks and function but do cost
more to procure), Q: Are CF (acronym for Compact Fluorescents) even "better"?
(yep, though cost even more to set-up initially, lamp cost, replacement,
energy all conserved in long term... per useful photon... and IMO looks-wise).
Q: Are there discernible benefits from mixing lighting "types" other than
appearance considerations? (yep, depending: organism mix (some really do
better with a modicum of "actinism" in their spectral preponderance..., some
evidence exists for 10, 20+k scintillation effects...) & the physical make-up
of your system. 
 	Let this be somewhat as a springboard for another go-round disc. of
light/lighting issues. A need for specifics? Other opinions, facts? A plug
from the "shop light" contingent? HQI and MH proponents? Other means of
photonic production?
Bob Fenner