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RE: Light Spectrum
Paul Westall asked, in APD #711:
> question about flourescent bulbs. I have read that "most" aquarium =
> plants prefer a buld with color temp less than 5300-5400K. But, many =
> people on the list seem to have great success with higher temp, bluer, =
> bulbs. In the past I have used 5500K metal halide which seemed to work =
> well. Do you think that 6500K flourescent bulbs are too blue for most =
> freshwater plants? Or, how about a mix of Chroma50 and Chroma 75?
Paul, this is only _my_ opinion, based upon my _own_ experience with plants
and different light sources. When I first started with the hobby (a long,
long time ago) I used incandescents (2X60W over a 15Gal tank), and I was
able to grow plants. Not very well, mind you, but they did grow - especially
Over the years, I have tried _most_ of the commonly available fluorescent
tubes (except HO and VHO) as well as 5500K Metal Halides. My experience has
been that provided your give them ENOUGH light, it doesn't really matter
that you use a specific spectrum bulb. Perhaps if you were trying to get
African violets to bloom, the spectrum might make a big difference, but in
an aquarium we are looking (generally) for vegetative growth and if there is
a high enough level of _any_ kind of light, the plants will grow.
I would suggest, that for all practical purposes, in a typical aquarium in a
living room, it is more important to get a bulb or a mixture of bulbs which
is pleasing to YOUR eyes. Different tubes provide a slightly different
"color" of light. You can see this if you see lighted tubes of different
types side by side. Chroma 50's are great, and they seem to have become more
easily available in recent years, therefore they are cheap too. Chroma 75's
are a little "bluer" (to my eye, anyway) but it still "looks" white. A
mixture of the two would be fine for plants.
What you DON'T need to do is spend mega bucks on $30.00 "aquarium tubes"
that are marketed by a number of companies. I like to get a bulb with a high
CRI (Color Rendering Index - Sunlight is rated at 100, Chroma 50's are 90,
Chroma 75's are 92) and a Color Temp. of at least 5,000K. That way, I know
that it will look natural to my eye, provide a full specrum of light (or a
close approximation of a full spectrum) to the plants, and not cost me an
arm and a leg.