# "WPG" thoughts



## Brian (Mar 14, 2006)

So last night I popped on a light fixture I pulled off a 20gal and I put it onto my 35gal. I turned off the strip light I had on there and just had the fixture on as "mood light" and then the thought hit me... 

Let's say you have a nice big bush of windelev fern and its in the middle of your 20gal as a centrepiece. Now let's say that the dimensions on the 20 is 24x16x18 (it probably doesn't work out that way but pretend it does ) and the 2 ft. light fixture provides enough light for the windelev to flourish, so 60 watts if you're going by 3 WPG. 

Alright, now let's say that you take that centrepiece and put it into the middle of a 35gal that's 36x16x18 and you take that same light fixture off the 20gal and put it over the centre of the 35gal.

So if you're going by WPG and you need 3 WPG to have your windelev flourish... in this case the light fixture would be providing less than 2 WPG over the 35gal but it would be providing exactly 3 WPG over the 20gal but the thing is... the height of both tanks are the same and the windelev is being placed in the exact centre of both the 35 and the 20 which means that the plant would be receiving the same amount of light even though the WPG is different... right?

I mean, the only thing that is different is that the plant has an extra 6 inches of room on each side of it but how would that effect the light it is receiving if the tank specs are essentially the same and the light fixture is being placed at the same place?


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## Pablo (Mar 27, 2006)

light doesn't magically float around and diffuse based on how much water its hitting. WPG is an attempt at helping stupid people be successful, kind of like inches of fish per gallon.

The only thing that's gonna matter is the amount of nutrients in the water, and water chemistry, and the distance from the light to the plant and how much of the plant gets light.


if you're moving to a tank that's the same height and you're positioning the plant identically to your light you will have no difference- unless the aquarium's water is very different. AFAIK 35/20 are both 18" tall in standard config.


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## Brian (Mar 14, 2006)

So then I am correct in assuming that there is essentially no difference in the light effect.


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## wtac (Mar 17, 2006)

You are correct Brian.

The WPG is a general rule of thumb _*assuming *_that lighting is spread out evenly across the entire length of the aquarium. In your particular case, that plant should not notice a difference in lighting, whether intensity or quality, using the same lighting system of the smaller set-up. Trying to grow a wide variety of plants where there is no light directly above is another matter .


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## Brian (Mar 14, 2006)

Thanks Wilson  and Pablo... lol.



wtac said:


> You are correct Brian.
> 
> The WPG is a general rule of thumb _*assuming *_that lighting is spread out evenly across the entire length of the aquarium. In your particular case, that plant should not notice a difference in lighting, whether intensity or quality, using the same lighting system of the smaller set-up. Trying to grow a wide variety of plants where there is no light directly above is another matter .


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