RubenD wrote:
Watts per gallon is the worst measurement for light just because of the
reasons you list. It does not take into account the depth of the tank
or where in the tank you are putting the creatures.


What is the best measurement for lighting then?

I supposed the coral under the bulb is the winner regardless of the
watts/gallon rule or the size of the tank, but how much light would be
acceptable? If I place the coral under the 30watts bulb, he'll be getting
not 6w but 30w, right?

What you think?



Watts is not a measure of lillumination. LUX is the measurement of
illumintation. Lumens is a measurement of light output.

therefore it makes no sense to ask if a coral would be getting "30w" of
light.

The difference between lux and lumens can be illustrated thusly:
LUX will decrese with distance from bulb. How much a decrease there will
be needs to take many factors into account - distance from bulb, what is
in between (ie: water, glass, etc) and even the spectrum of bulb.

LUMENS will NOT decrease, since the bulb is still just as bright no
matter how far you are from it.

Lumens is how much light gets put out, LUX is how much light is reaching
what you are trying to illuminate.

What we SHOULD all be using is LUX. It would make sense to say things
like "this crocea clam needs about 32000 lux", but I have never seen
that used.