logistical graph lighting?

[Milton Friedman]

I came across a interesting website describing the relationship between amount of gallons and the amount of watts of lighting (I'm assuming Florescent) Takashi Amano uses in his tanks. I'm curious to know, why for example in a 5 gallon tank, he uses 6 watts per gallon, yet as you follow the logistical graph, only 2 watts per gallon on a 500 gallon tank? Could someone plz explain why that is?

http://www.fitchfamily.com/lighting.html

 

[slipknottin]

plant A needs 10,000 lumens to reach its saturation point.

Put the plant in a 1 gallon tank or a 10,000 gallon tank, it still needs 10,000 lumens.

A 10 watt light might put out, lets say 500 lumens. Over a 1 gallon tank, this is the equal of 10 watts per gallon, but is not enough light to satsify the plants need.

On the other end of the spectrum, we have a 10,000 gallon tank. Lets say a 150 watt halide puts out 10,000 lumens. Put the plant up near the surface and the light directly over it, and you meet the plants requirements. Thats only .015 watts per gallon.


This is why watts per gallon is not a truly accurate measurement of lighting. Better is lumens/sq ft or sq meter, or even better PAR or ppfd per sq ft or meter, and you should always consider the depth of the tank too.

 

[got_nailed]

“by calculating watts per 'estimated surface area” I just read the article and parts of it seam to make good since but yes it dose against most of the WPG rules I have read.

The 2 main factors that seam to play the biggest roles are the surface area and the depth of the tank. The deeper the tank the more light will be required for the plants to be happy at the bottom of the tank. I would think some one would come up with a formula that would take the surface area and the depth of the tank to come out with a better “rule of thumb” for something like this.