Watts per gallon

[stephane.savard]

Maybe someone could help clarify something...

I keep seeing people mentioning specific watts per gallon numbers for lighting. I understand what it means, but what's got me confused is that wpg is quoted without ever taking into consideration the actual lighting.

Say I have 2 watts per gallon of lighting on three different tanks, one using T8 fluorescents, one with T5HO lighting, and finally one with metal hallide. Lets suppose that each of them gives off the same color temperature...

So is this 2 wpg lighting actually giving off equalivant light for all three tanks?

If not, how can I understand what is truely meant by a specific amount of light measured in watts per gallon?

[Wild Turkey]

So is this 2 wpg lighting actually giving off equalivant light for all three tanks?



Nope, as you seem to suspect there are other variables. The smaller diameter bulbs put out more light per watt t5 is the smallest atm. Depth of the tank also comes into play, tannins in the water, a lot of things can effect how much light the plants receive relative to wattage. Wpg is a good way to judge without asking a zillion questions though. The only way to be sure you are using the best light available would be some kind of water proof lightmeter....and im sure thats not cost effective. The plants themselves are effective meters.