[APD] Power Compact Bulb Useful Life: 12 months max

[Dave Millman <dave at tactics_com>]

My tank looked great for the first year. I sold lots of plants at the LFS 
and gave them away online, everybody was happy.

The tank went steadily down hill during year two. The only good thing about 
that year was that I continuously improved all of my nutrient and 
cultivation techniques so that I'm doing everything pretty much perfectly 
now (50% weekly water change, Tom Barr's estimative index method). But the 
tank was still pure greenwater for months 22-23. Daphnia helped, but it was 
too much of a pain to keep them in the tank.

So I borrowed a UV filter to clear the tank, and followed Tom Barr's advice 
to start at the beginning: Light.

I bought four new 55W bulbs from AH Supply to replace my 23 month old ones. 
Guess what: Using the light meter in a professional video camera, I 
discovered that the difference in brightness between the new and old bulbs 
was much more than one f-stop. This means the old bulbs were putting out 
less than half the light the new ones were, at least in the frequencies to 
which the light meter is sensitive. While this imprecise test ignores the 
plant's spectral requirements, it still says to me that my tank went from 
over 3W per gallon to under 2W per gallon, while I was still dumping full 
nutrients in there. No wonder I had green water.

Now the new bulbs are in, and the plants are pearling like mad. I haven't 
seen that in nearly a year.

If anyone out there has the expertise and equipment to properly measure the 
output of my old bulbs, I would be happy to send them to you if you will 
publish a comparison with new bulbs. AHS or another vendor might even 
contribute a new bulb for comparison.

I can't imagine why somebody would spend premium money for a CF fixture, 
then not replace the bulbs every 12 months.

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