08-04-2012, 03:32 PM
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Originally Posted by Quantum
PAR is only relevant to plants and other photosynthetic organisms (Photosynthetically Active Radiation), it is only indirectly related to human vision (lux and lighting design, etc.) because for the most part light that is photosynthetically active coincides with the visible (to humans) portion of the electromagnetic spectrum.
There are conversion factors that can be used to convert lux to photon flux, these are based on generalities and would be approximate: lux(0.013) for 'cool white' fluorescent according to one source.
PAR is a quatitative measure (#photons/area/time), but how would you know how many photons would be needed? You would have a number, but would that be too many photons per sec or not enough? It also would not tell you what specific wavelength light is produced, only that it is between 400 and 700 nm. You would need to know the spectral output of the source to determine if it is good for plant growth.
A single 18" T8 tube is adequate light to grow a lot of types of plants in a 10 gal aquarium. One suggestion though, if your tube is the 8000K one that comes standard with Aqueon fixtures, it may be worth it to get a better tube. One around 6500K will provide good light for plants and produce a whiter light rather than the pink hue those produce.
Quantum, several other people have remarked about the Aqueon tube that comes standard with their fixtures as having a color temperature of 8000 K and a pink color. I think that I have a different tube that came with the 10 gallon fixture - the apparent tube light color is white, no pink, and it gives a perfectly realistic color to the plants. I'm stumped. The tube is labeled "full spectrum", although it probably has a greater output in certain areas of the spectrum. I wish I could get some confirmation that my tube is more like a daylight tube.