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Re: [APD] Re: Lux

Well it's more like the guy that used the timex watch that
lost two minutes a day because the "more accurate" Bulova
chronograph he owned he could not find.  Perhaps it's fell
in the white bucket with the water that was, what color?

If you don't want to rely the wpg rule of thumb and you
want to put just the optimum amount of light on your plant
-- and that might not be what you want -- this is some of
what you need to find:

The PAR spectrum requirements for the plants you intend to
The PAR output graph for the bulb(s) you intend to use.
The reflectivity of the reflector or bulb housing you
intend to use.
The turbidity of the water in your aquarium.
The distance between your plants and the light source
(well, you'll have to settle for a max, min, or median, or
mean here.

You're not likely to find all of these and if you do, some
of them probably won't be ratings based on standardized
measures.  For example, plant requirements you'll find 
usually say low, medium, or high or something vague like
that. I don't recall anyone recommending a particular lux
dosing for Echinodorus bleheri, for example.

But instead you can go with some rules of thumb that work

RE something that measures light energy at the bottom of
the tank, that would be a waterproof light meter
(especially if it is weighted for PAR) or for comparison
purposes, put a mirror or white refelctive surface in the
tank and measure the light reflected off of that by using a
non-waterproof lightmeter outside the tank.   But even if
you know the light output of your lamp/bulb assembly, what
use is that unless you know how much light you want?

So one might ask, "What is the optimum light level for
plants?"  Actually, that's not a very well formed question.
The syntax is okay but logically, it begs a lot of
questions. I'd need to include something about goals for
the question to be useful. Something like, what's the
optimum amount of light to maximize the rate of growth
while avoiding algae and not dosing ferts other than fish
food - - -  something more like that.  And the answer would
undoubtedly be that it depends.  There's no magic number
for the right amount of light.  Gardeners grow plants
successfully at 1, 2, 5 and more watts per gallon -- and
I'd bet the lumens, lux, PAR, is about as broad a range
too. In part, your nutrients need to fit your lighting and
vice versa but I don't think you'll find any simple
formulas for this. And you might decide you don't like to
prune too often, so fold that in and the optimum light
level changes again.

Rules of thumb are pretty useful and lead to lots of
learning, especially about one's own gardening techniques,
aptitudes, and tolerances.

Good luck, good fun, don't drive yourself nuts on the fine

Scott H.

--- Billinet at aol_com wrote:
> Scott said, in part, 
>   > Actually, watts per gallon is the *most* useful
> because,
>   > although inaccurate, it's readily availailable.  . .
> . 
> That reminds me of the story about the man who was found
> searching for his wallet at night under a street lamp. 
> When he was asked where he'd lost it, he responded that
> he had dropped it in the middle of the block.  Why was he
> looking down here, then?  Because the light is better, he
> answered. <g>
> What I am looking for is something that would measure the
> "light energy" at the point at which it is often most
> needed, at the bottom of the tank.  Everybody knows that
> tall tanks require more lighting than short ones with the
> same capacity, and that very large tanks need fewer watts
> per gallon than small ones.  "Lux", or something like it,
> would quantify those differences and eliminate a lot of
> confusion.
> Bill
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