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Re: lumen ratings, watts/gallon

Hoa Nguyen wrote:

> Most 40W shop lights are rated at around 2000 (initial) lumens.  While the
> high efficiency 40W bulbs are around 3500 lumens (Philips Advantage X: 3700
> lumens, Ultra TriLux: 3350 lumens).  That's quite a spread.

Lumens/watt varies with the age of the light.  A new cool white might
produce more light than an old Triton (for instance).  Given all of the
other sources of variation, the difference between 2000 and 3700 lumens
isn't all that stunning.  The presence of absence of floating plants in
your tank will cause a bigger variation in the average light intensity.

My 55 gallon tank was once equipped with two Advantage X and two
Ultralumes - both high lumen/watt lights with big peaks in the green band.
When I switched the tank to two Grolux and two Daylight Ultras (neither
with the green spike) I got much better growth, even though the tank
appeared to be darker than before.  The lumen rating is misleading.

> So the watts/gallon rule remains a rule of thumb.  I think you can use a
> lower ratio if you use higher-efficiency bulbs or if your tank is large and
> shallow, and vice versa.  And until there is a definitive result on which
> wavelengths are best for aquatic plants, I'd stick with a full spectrum
> bulb with strong output in all three red, green and blue regions.

It's definitely just a rule of thumb.

Incidentally, the triphosphor lamps (Advantage X, Triton, et al) are *not*
full spectrum lights.  Their light consists largely of three spikes, each
in a narrow band - one in the violet or blue, one in the green and one in
the orange or very near red.  That gives them a nice color rendition
because its close to the way our eyes sense color.  All of them have big
gaps in the spectrum, and I only recall seeing one manufacturer's spec
that showed very much true red light.

Vitalites and a few similar brands are actual full spectrum lights - they
produce a fairly even distribution of light from infrared through
long-wave ultraviolet. GE Daylight bulbs and their look-alikes are wide
spectrum lights with a broad distribution across most of the visible

And of course, all of these lights can grow plants, though your success
may vary.

Roger Miller