Let's assume for a moment spectrum doesn't matter and there's no great
difference between the worst (soft white) and best (triton) tubes. An
article in the kib says philips tested this and found a 10% difference
in plant growth from worst to best - insignficant.

Twenty years ago in these newsgroups people began talking about
different colors of light and how they affect plant growth. To
this day there is no such thing as the "right" spectrum. If there
was somehow it's evaded the notices of what much by now be millions
of aquarists over two decades. I can believe I'm this dumb but I
seriously dount the collected wisdom of all aquarists here is.

I doubt as well there's any question 80 watts of 2' fluorescent
will give better results than 20 watts of 2' fluorescent light.
Intensity matters.

In _The Optimum Aquarium_ Horst and Kipper note that "any fluorescent
tube light without a reflector should be rejected - 30% of the light
is wasted". Being a cylinder, there's no point in an equal distribution
of light pointing up as down into the tank henct the need for a reflector.

So, a 20W bulb putting out, as an examlpe 1000 lumens will only shine
700 lument into a tank and you'd need a larger than 20W tube w/o a
reflector to get as much light into the tank as a 20W tube with
a reflector.

Now, say you removed that 20W 2' light and put in a single 24watt
screwin in the middle of the tank. More watts, but a simple
test with a light meter in a plastic bag shows that at the ends
of the tank you don't have the same lux or lumens there as you
did with the 2' tube - the tube ligts evenly acros it's length,
the screwin blasts light in a radial pattern and all those spirals
casue strike back - light is bounced around everywhere losing energey
(dramatically) every time it bounces.

So, the problem with screwins is not really that they don't put out
much light, they do, but you just can't focus it and get it down to
the plants leaves very well.

Where screwins really shine (haha) is over small tanks where you can't
put a tube (Elaine, I doubt your Mayace problem is spectum; put the old
bulb back in and see what happens) but my opinion is because they
waste so much light you need to make a more or less continuos strip of
them, ie 4 of them to replace a 2' tube to get the same amount of light
*on the plant leaves" as you would with a 2' tube and at that point
you're wasting so much energy ($$$) and generating so much extra heat
that it seems to me like a very diminished return.





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