For growers under lights

[matthewjohn]

When is a good time to change the tubes in a flourecent set-up. I know that the tubes lose there effectiveness after a while but, how long is too long. My lights tubes have been in for about six months and I was thinking of starting to change them out. Foot candle reading is about 750 at about two inches away. The plants look healthy, mostly phals but a few catts till they can go back outside. One phal has started to spike again which makes me think the tubes are still good and I might just be wasting money. Any input would be good.

[mayres]

In the "for what its worth" department.....
Where I work we are REQUIRED to replace the fluorescent tubes in our insect-o-cuters every six months to retain maximum effectiveness.
I checked mine with a light meter too and got a similar reading from 3300 lumen tubes. When they were new they were right at 1000 footcandles at the bulb, but 750 after six months. So far my best guess is that they might be 10-20% reduced at six months versus new bulbs. You might not think this excessive and choose to wait to replace them in a year or so. My thought is that these plants need all the light they can get when you are talking fluorescents - if you are trying to maximize the effectiveness, changeouts at six month intervals is not unreasonable. Funny how the sleeves on the tubes say "good for six years". That may be if only used a few hours per day, but not when used 16 hours per day - IMHO. Good luck! mike

[Cynthia, Prescott, AZ]

One commercial Phal grower who uses fluorescents, said to change lights every Sept, as the increase in light is what the Phals, and from my knowledge Dens too, expect every winter. It is either because the skies are clearer in winter, or that the trees they grow on are deciduous, and both may be in effect for some areas.