# How to determine WPG



## PlantsAndMe (Apr 3, 2005)

How do you determine the WPG? I have a 10 watt in a 5 gallon. would it be 2 WPG?


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## Hilo-RnM (Dec 26, 2004)

I read some where that it's 3 wpg. I also would like to know which is correct.


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## Erirku (Oct 5, 2004)

It usually depends what your aspect of an aquascape is! If your tank is a highlight tank (Ex: riccia, glosso, rotala, etc) then the main point of good WPG would be 3.0-4.0 WPG. Low light tanks (Ex: crypts, java moss, anubia, etc) 1.5-2.5WPG is good. IF I'm wrong, correct peoples. But hope that helps, and have fun aquascaping.


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## Laith (Sep 4, 2004)

10w over a 5 gallon is 10 divided by 5 = 2wpg.


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## New 2 Fish (Dec 31, 2004)

Rexgrigg.com says that the WPG rules breaks down over smaller tanks, that you need to know the lumens per unit of area. However, I wasn't able to find the lumens for my lights to calculate...


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## gnatster (Mar 6, 2004)

For a simple WPG Laith has the example correct, simply (Total Lamp Wattage) / (Tank Vol in Gal) = Watts Per Gallon. 

This is a good very basic rule of thumb. I can't stress the "very basic" aspect enough. 

The rule like many others does not fit all situations but is a good place to start. Being this is the New to Aquarium Plants forum it's the place to delve into the deeper aspects, thats better left to discussion in the Lighting area of the Advanced topics.


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## trenac (Jul 16, 2004)

_What type bulb do you have_?... The WPG rule is based on florescent bulbs. If you have PC bulb you will have a little more and incandescents only produce heat. You also have to remember that the WPG breaks down for smaller tanks. Here is a link on the break down... http://www.rexgrigg.com/mlt.htm


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## Bounty (May 18, 2004)

Im now running 8 55watt 10K fluro tubes on my 119. going by that simple rule that would make 3.6WPG?


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## PlantsAndMe (Apr 3, 2005)

If my calculations are correct: 8 x 55 / 119 = 3.69 :smile:


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## carisma02uk (Mar 11, 2005)

*wpg calculations*

hi the correct calculation to find your wpg is times the length by width of your tank to find you sq footage and then divide by your total watts of lighting. remember that aquariums with reflectors may have more or less depending on your type of bulb.


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## hoppycalif (Apr 7, 2005)

*WPG Formula*

WPG means watts per gallon, so it is always the number of watts of light divided by the number of gallons in the tank. But, it is a guide only. Obviously a bare T12 fluorescent bulb with no reflector, held 6 inches above the water in a very deep tank doesn't provide as much light as a T8 fluorescent bulb, in a very good reflector, held only two inches above the water in a much shallower tank. I know the original WPG guides were intended for the T12 bulbs in standard white reflectors, so you can estimate how much better your setup is to get a better feel for the effective watts per gallon you are using. Then, it is still just a general guide!


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## puneit (Apr 8, 2005)

I would like to know that if I am planting only one corner of my tank, then does WPG calculation hold good, as the plants are not spread all over the tank. What do you suggest in that case.
Moreover, is it just WPG that is significant, as I have read that color temperature and wavlength are also important. 
I use 18 W Compact flourocent light in my 20 gal tank, in which the light I have placed just above the plants. Is such setup, going to give good results?
I am also using a DIY yeast type CO2 reactor fed to the intake of power filter.


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## ardvark (Feb 26, 2005)

Hi puneit,
I realize that everyone has their own sense of aesthetics and their own goals but could you help me to understand something? Why would you go through the trouble of setting up a tank and DIY CO2 etc. only to put plants in only one corner of the tank? Most forum members endeavor to maximize the plant bioload in the tank so your layout seems rather strange if you don't mind my saying. What do you have in the other corner or in the middle of the tank that precludes putting plants there as well. Is it just a personal preference or is there some other issue? Will you just put a single big plant in the corner or several?

It's my guess that the wpg rule assumes a more or less random or even distribution of plants in the tank so that the plants are illumintaed from all angles and shading is minimized. If you have a few plants and if for example their upper leaves shade those directly below, not having a light shining from a more oblique angle may have a negative impact on those lower leaves. Thats just a quick geometric excercise, nothing definitive. So following this train of though it would depend on so many variables such as the actual size, quantity and shape of the upper leaves, type of plant... Suffice to say that more shading would occur if your light is only on one side. WPG is only a rule of thumb so there is no way of predicting the results with your proposed configuration. Just try it and add more light if needed.

Let us know the results though. That will add to everyones knowledge.

Cheers,


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