> From: krandall at world_std.com (Karen A Randall)
> In which case, unless I'm missing something,  it has left the 
> tank, and ain't coming back.  Therefore it is, for all practical 
> purposes lost to the system.  Which is exactly what I said.  In an 
> EMPTY tank you might not lose any light, but in a PLANTED tank, 
> you most certainly do.  And the deeper and more heavily planted 
> (or otherwise decorated) the tank is, the more light you are going 
> to lose.  

which is what I mentioned in my original post as the third item.  Go back
and read it.  I said 1) light goes somewhere between inverse square,
inverse line, or not at all, depending on the source and reflector; 2)
light gets internally reflected by the walls of the tank, which would
cause it to be theoretically depth-independent, BUT 3) it gets absorbed by
the surface area of plants, rocks, algae, etc that it hits.  If you have a
tank with nothing but E. tenellus growing as a carpet on the bottom, there
will not be much difference between heights, but if you like to grow
plants up the sides, or don't clean your glass much, then there will be a
difference.  OK, I didn't mention the bit about plants reflecting the
light at random angles so that you can see them, but my third point was
that effectively once the light hits the plants, it's out of the system.
Same as your point.  Why slam one paragraph when the overall post
supported your theory?  I was trying to explain all the effects, and total
internal reflection IS AN EFFECT that does tend to drive the system
towards depth independence (and away from inverse-square law dropoff.

  - Erik

Erik D. Olson					         amazingly, at home
eriko at wrq_com