Here are my thoughts on various fluorescent bulbs. The size of the
lamp (bulb) is important but not as important as the electronics and
the phosphors used to coat the inside of the glass.

"T" (as in T8) stand for "Tubular" and the number stand for "eights of
an inch in diameter". Therefore a T-8 is tublular and one inch in
diameter. T12 is 1.5 inches and T5 is 5/8". T8 and T5 operate at a
higher frequency, which results in less flicker and high light output
per watt of energy input (efficiency). It also means you have to use
a ballast designed to operate that type of lamp. So you can use T8
bulbs in a cheap shop light (i.e. fixture)ONLY if it came with a
ballast that drives T8s or you change the ballast. The lamp may light
on a mismatched ballast, but it not operate correctly (per specs) and
may shorten its life. (HO and VHO are high output and very high
output T12 lamps that have been around for years, but are not as
efficient (in terms of lumens per watt) as regular T12 or T8/T5.)

Compact Fluorescents (CF) are usually U-shaped or may be another shape
(e.g.spiral), and are more efficient than tubular lamps. There is
another bonus: because they are smaller, it is easier for
fixture/reflector designers to get the light out of the fixture into
the aquarium. As a result, you will get more light into the tank with
the same wattage of CF than you will with T8s or other tubular lamps.
Again, the ballast and lamps must match to get proper operation. Of
course CFs are more expensive to purchase too.

The color temperature and color rendering, among other light quality
factors is largely affected by the phosphors coating the inside of the
lamp. Generally (oversimplified!) the new lamps like T8, T5 and CF
have high quality phosphors -- usually tri-phosphors -- that provide
the highest efficiency and best lighting quality (a broad term for
sure, but generally I mean color rendition and control). Some T12 have
similar phosphors, but not the standard 40 watt lamps you get in a
shoplight.

In summary, if money is no barrier, CFs with electronic ballasts, good
quality, well designed reflectors, and triphosphor lamps in a color
temperature (e.g. 6700K, 5000K) that suits you preference for warm vs.
cool overall color will give the best results and most light per watt
(among the flourescent options - MH have other attributes that
complicate the topic). There is one caveat: various lamp
manufacturers tweak the phosphors to provide many varitions on the
light spectrum emitted. Your choice among these are largely based on
your personal preferences for how you plants and fish look...currectly
there is more variety in lamp choices in T8 than in CF. So T8 is a
good option too, although slightly less efficient than CFs. Since CFs
are inherently more efficient, I suspect that will change as more
people start making specialty CFs.

I hope this helps. BTW, I don't sell any of this stuff and I am not
affiliated with any manufacturer/vendor.




Trygve Lillefosse wrote in message . ..
t8s are a newer design...part of it is the fact that they are smaller, but I
think they are designed better than the original t12s...there is a reason
that most offices are going towards t8s...more efficient, less energy
used...and they tend to degrade less over time...

There is even a new design on the market, count on it to be the next
standard. T5, they are thinner than T8 (as the number refers to their
physical size) and also gives more light.

As to now it's mostly used where realy good light is needed as in
workplaces. (drawing boards etc.) After what I'we heard they should be
able to compee with mercury-bulbs for reef-tank use.

SEE YA !!!

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