05-13-2009, 11:30 AM
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Won't comment on t5 as I have no personal experience. But as for the best light for a planted aquarium--full spectrum. Plants mainly require light in the blue range (to stimulate photosynthesis which is their growing process) and to a lesser extent in the red range. [Takashi Amano has a regular column in TFH and in one of them a couple of years back he explained this.] However, a tank with blue and red lighting looks purplish and "ghostly" and the plants and fish do not display natural colours. To appear "natural" the light must be a balance, and full spectrum achieves this; it replicates the sun at mid-day, and the plant greens look natural as do the fish colours.
With more than one light tube you can mix types, which is what I've done. One tube is straight full spectrum, the other is just a bit more blue than full spectrum. The plants are thriving (look at my photos) and the look is natural (the photos are a bit "green" but that is my cheap camera, not the tank lighting). I find the full spectrum enhances reds a bit, and the cooler tube enhances blues a bit (and promotes plants as I said) so it is a nice balance visually and practically.
Photosynthesis occurs only in daylight and is dependant upon the intensity and duration of the light. Intensity is expressed for our terms as Kelvin, and most aquarists recommend a tube with a rating of around 6500K (I think mine are 6700K). Sunlight peaks in the blue range of the spectrum, and this light is used by all plants (and algae), as is red light though to a lesser extent. Green light is reflected by the majority of plants, which is one reason why incadescent bulbs (poor in blue but often higher in green/yellow) are less satisfactory over plants. Blue light also penetrates water better than the other colours, which aids the lower plants that need it.