[parkinsn]

The general idea of that artical is correct and what you are saying makes sense. However that article was printed in 2000, the tecnology has changed a fair bit since then. For a standard F54T5HO @ 32 degrees (ambient temp in degrees C) you will get 100% relative light output, @ 45 degrees (ambient) you will get 96% relative light output. You will not be able to see a 20% change in relative light output untill you hit on the low end of 22 degrees (ambient) and the high end of 57 degrees (ambient). They have designed T5's now for replacement's of 400W metal halide in warehouse applications, (if you have ever changed a lamp in a homedepot type warehouse it is hot as heck at the top of the roof usually 45-50 degrees C in the summer)

If its a 20% increase in lighting your looking for i dont think your going to see it without a PAR meter or even get more that about 2-4% increase by droping the temp a few degrees. As for the temp going up in your canopy, i would say that is due to the fact that you are creating more heat with your fan motor in turn blowing warmer air into your canopy

In summery the new style ballasts and lamps are all designed for higher temp's, but it still remains true that T5's do not like cold. On that note you can buy "extreme tempature rated lamps" which will get 100% relative light output @ 32 degrees C to 60 degrees C (ambient temp). Although im not sure if they are available in the color temps that aquarium lamps come in.