WPG, What is the truth?

J

jfennimore

AC Members
Feb 22, 2005
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Wasn't sure how to title the thread, but now that you are reading it.....The question always is "How many watts per gallon do you have?" What is the standard for 1 watt? Aren't we more interested in lumens? If so, when someone gives WPG they really mean that so many lumens are provided by a given watt, but since we purchase bulbs by watts, it would be easier to provide WPG as a standard? For instance, a given 32 watt T8 bulb could produce 2800 lumens, while a 40 watt T12 might only produce 2200 lumens. By using just the WPG theory, I would be better off with the T12. But we all know that this isn't the case. I have also been trying different ODNO techniques, and was wondering how this type of lighting would fit into the equation as well. Lastly, what about size of the bulb? With power compacts you have "more" light in a smaller area, versus the length of a longer bulb. What kind of impact does that have?
Thanks.

Jeff
 
First, what are you trying to establish with your lighting? FO, then the lighting is mostly for your viewing pleasure, and it won't matter lumens versus spectrum versus watts. For plants--all depends on what you want from your plants. I have moderately planted, low light/low tech tanks, so none of the above are particularly relevant. For a reef tank, it's a totally different game.
 
AFAIK, the WPG 'rule' (recommendations for plant growth) is based on T12 NO fluorescent lighting. It doesn't really work with tanks much smaller than 20g or much larger than ~75g - you'll need more WPG on a smaller tank, less for a larger tank.
Agreed, watts aren't really a way to measure light output, but because the guidelines are based on a specific type of fluorescent, you can use the wattage to determine how much light will be over the tank. As I understand it, PC provides 2-3 times the useable light of a T12 bulb (per watt).
If you do a search of the planted forum for 'WPG' you'll find lots of posts where this is discussed, which may help :)
 
CO2 supplementation? Fast growth? How densely planted? This is why this is such a complex topic, and why we try to simplify it by using something everyone can easily identify--WPG. I have a 5 here at work that has about 3 plants (2 medium sized crypts and 1 large and ropy anubias plus java moss), under 8W total...But I don't want fast growth, minimal supplements (monthly dose of Flourish), and both plant types are happy with slow growth.
 
As said it is a basic guideline. I work a lot in the world of extra tall tanks, and have to expand my requirements from the basic rule. on the flip side I work with open tops, so no distortion or even the smallest bit of shadowing. WPG really just becomes a baseline to start from and the plants teach us from there. To give you an example, my 15g runs 65watts PC + 15 watts no florescent. my 10 runs 28 watts pc + 15 watts NO flo. My 115 (31" high) runs 240 watts NO Florescent. all three do well with Co2 and heavy ferts. But the light rules and the things I've read only aplly marginally to any off the three.
Dave
 
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