"Aaron Hicks" wrote in message
...
mg queried thusly:

I was in WalMart today getting some replacement bulbs - I use 4 2'
flourescent bulbs for one set of plants - when I noticed lumen output
varied widely between bulbs. Aquarium/Plant bulbs had 750, Home and
Bath bulbs had 1250. And for the same space, I could get 3 or 4 times
as many lumens with compact flourescents - the circular halo-looking
things. All at 20 W apiece.

More lumens means more light, right? Is spectrum a factor, or for the
same price why wouldn't I just go for the highest lumen count for the
space? What am I missing?

Intensity is certainly one factor, and it becomes important with
plants that demand a lot of light.

However, another factor is photosynthetically active radiation
(PAR), which is light that plants can absorb and use. A good web page on
the whole subject is he

http://www.aquabotanic.com/lightcompare.htm

There's an interesting table about 3/5 of the way down on PUR
efficiency ratio in uE/s/watt that should be kept in mind when comparing
"Gro-Lux" to regular fluorescent tubes. They really aren't worth the extra
expense.

The e-mail address in the header doesn't work. Send no mail there.

-AJHicks
Chandler, AZ



Also, when comparing output of compact fluorescent bulbs, be sure to read
very carefully. Lots of them use alternative measurements to express outputs
and use confusing language comparing the output of regular incandescents to
CFL bulbs.

I just recently purchased some CFLs rated at 3500 Lumens for an 85W bulb. I
honestly doubt you can find a 20W bulb that will put out as much light as
you say the packaging indicated.

Sam