Watt/Gal or Lumen/sqft?

[XnSdVd]

If you ask me, Lumens per sqft seems to make ALOT more sense than watts per gallon. Especially considering you're aiming to light the gravel and plants, not the water...

And lets not forget that wattage isn't a measurement of light produced but the ammount of power used by the bulb. MHs produce something in the range of 120++ lumens per watt while FLs are more in the range of 70 - 80 lumens. That's a HUGE difference. And consider that we usually deal in 10s of watts or 100s in the case of larger aquariums...

Gurus to the rescue?

[hwchoy]

W per gal (US) is merely a rule of thumb, especially for smaller tanks where this figure can go as high as 10W per gal.

[tawauboy]

this watt per gallon figure is mean as a guide.
lumens per sqft will still be a guide.
there are may factors such as,
i) distance between light source and water surface
ii) distance between light source and gravel
iii) type of plants
iv) amount of surface ripple
v) ...

[XnSdVd]

Surface ripples? how on earth do you account for that?

[Justikanz]

Surface ripples can 'cancel' some of the light...

I also always believe in measuring the amount of light per area rather than per volume of water... But all are just guides... It really depends on the plants and such... Light also diffuses IN the water and absorbed BY the water. Amount of fine particles in the water also affect the amount of light needed...

[solonavi]

Lumen is too dificult to determine unlike Watt is fitted.

If u have a gd reflector, ur lumen will increase alot. Same for ripples, it will refract/reflect some lights out of ur tank.

Also lumen will decrease over the life span of the tube. Thus a new tube will have the highest amount of lumen. This means that lumen is a gd way to determine if u need to change tube already.

Cheers
JC