RE: best fluorescent

["Eric Wahlig" <ewahlig at earthlink_net>]

Paul was asking about fluorescent tubes. He states: "I would like to get
some advice on what are the best florescent bulbs for growing plants. I'm
setting up a 50 gallon freshwater tank with a twin tube fixture and with
all the different bulbs on the market I'm not sure what to use. I have had
good results with a TRITON bulb in the past and will probably use one with
this tank. What other bulb would pair up with the TRITON to give me the
spectrum I need?"
 
Well, you did not state what wattage or length of fluorescent lamp you are
using but I will guess that you are using 36 inch T12 lamps as that is what
most twin tube fixtures are designed to use. Now, to make short work of a
very long and debated discussion (check the archives) I would say that the
exact spectrum is not that important as long as the lamp is designated as
"full spectrum" by its manufacturers. Fortunately, plants are not nearly as
demanding about color temperature or the individual proportions of the
three phosphors that comprise the "full spectrum" color temperature as are
photo-dependent
marine organisms. Personally, I use either the GE, Phillips, or Sylvania
brands with a 6500K or 7000K color temperature simply because I like the
"whiteness" of the light and they are readily available at reasonable cost.
There are many people growing plants under ordinary "shop lights", Mercury
Vapor HID lamps, Sodium HID lamps, and Halogen incandescent lamps. I think
this proves that plants are very adaptable at utilizing different spectrums
of light to the best of their ability. However, this ability is directly
related to other environmental parameters. Light intensity is the main one. 
 
The inexpensive "shop light" fluorescent lamps generate a spectrum heavily
weighted in the green/yellow band of the visible light spectrum. Mercury
Vapor HID lamps are heavy in the blue band and Sodium is in the red/orange
band. Halogen is just a little whiter than ordinary incandescent. Although
their spectrums differ dramatically, they are all able to grow plants if
the light they produce is intense enough. High Intensity Discharge(HID)
lamps and Halogen lamps generally are more intense by design. I should say
that the shop
lights aren't any more intense than other fluorescent lamps unless there
are more of them or they are overdriven. Even the best (and most
expensive) "balanced spectrum" lamp will not grow plants if it is not
intense enough and this leads me back to your original post.
 
If you intend to have a low light level tank that will house ferns, mosses,
Anubias, etc. (plants that generally tolerate living under a heavy forest
canopy), the twin tube strip light you currently have will probably be
enough. If you want to grow a wider assortment of plants or red pigmented
plants then
I suggest you increase the intensity of light by adding another light
fixture rather than supply a refined spectrum of low intensity light. If
you are not going to increase the intensity then the spectrum of light may
be more important. To utilize low light levels efficiently, the plants must
depend heavily on favorable conditions of the other environmental
parameters such as nutrient supply and ratio. If you don't have a CO2
system of some kind then this can really help. An interesting article on
the subject is: CO2, Light, and Growth of Aquatic Plants by Pedersen,
Christensen, and Andersen, PAM, Spring 2001. I can't find a link or
reference to online publication so I hope you can find it. 
 
If you really want a nice lamp that is specifically designed to support the
photosynthetic needs of living organisms then I would check out the
Verilux lamps. This supplier
<http://www.1000bulbs.com/shopping/shopdisplayproducts.asp?id=68&subcat=464&;
cat=Verilux+Fluorescent+Tubes> has them and they give a significant price
break if you order by the case. I have not delt with them.

--- Eric