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Re: Lighting and Lux


Lux, or illuminance per square meter, varies dramatically with the distance 
from the light source, inversely by the square of the distance, as a matter 
of fact.  It can almost disappear at the bottom of a deep tank.  That's why 
20 watts can grow glosso beautifully in a six inch deep tank, and not at all 
in a 15 inch tank, both with the same surface area.

It would be most useful to have a table that would show the lux that is 
produced by various bulb and reflector combinations, at distances of from, 
say, two inches through 20 inches from the light source.  I think that would
just about eliminate most of the lighting questions that we see and eliminate 
a lot of questions about "how many watts per gallon?" and "what is the best 

Has anyone seen such a table?  Would it be hard for a knowledgeable person to 
construct one?  I'd think it could be done either mathematically or 
experimentally, the latter with a waterproof lux meter and a flexible neck.