Watts per Gallon? Why not Lumens?

[Pszemol]

There is a common term in use for a light demand in aquarium... People recommend at least 3-4W/g to get photosynthesis working.

It does not sound right for me to express amount of light in watts. Are all light source equally efficient to prove usage watts/gallon? Does the 100W HQI produce the same amount of light like 100W fluorescent tube driven by old style 60Hz ballast or high-tech power-compact driven by an electronic high-freq ballast? Probably not...

So why not use lumens as more precise light units?

BTW - how much more efficient power-compacts are in comparison to the old-style fluorescent tubes powered from the standard 60Hz power source?

[reefdope]

To some degree I would agree with you, but then why not use Lux which is actually a measure of illumination and not a measure of flux?

Lumens is the unit of luminous flux in the International System, equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.

Lux is the International System unit of illumination, equal to one lumen per square meter

Oh the questions we have to ponder……

[PerryinCA]

Even lux isn't appropriate as is measures visible light and not light as it pertains to photosynthesis. This is why you see so many people jumping all over the PAR / PUR wagon. Its really tough to make any recommendation without being able to test surface values of PAR.

-Perry

[reefdope]

Perry,

Doh, your absolutely right....I actually knew that (or at leaste have been told that) but forgot....My Bad!