Lighting 2 watt per gallon rule - The Planted Tank Forum
 
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post #1 of 4 (permalink) Old 10-17-2007, 08:36 PM Thread Starter
 
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Lighting 2 watt per gallon rule

I am a little confused by this rule. Watt is a measure of energy consumption. What kind of light bulb does this apply to? Can anyone tell me what 2 watt per gallon translate into in lumens.

I found this chart on Wikipedia (http://en.wikipedia.org/wiki/Compact_fluorescent_lamp) that translates watt figure into lumens for different types of bulbs
so for example 60watt incandescent, 13 watt compact fluorescent and 30 watt Halogen bulbs all produce the same 865 lumens of light

Specifically I use compact fluorescent bulbs to light my 29 gallon tank - how many watts of compact fluorescent lights do I need to achieve good light levels.

Thanks,
Lev
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post #2 of 4 (permalink) Old 10-17-2007, 09:00 PM
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loty, just as you noticed, this watts per gallon "concept" is not something you want to follow. too many other factors -- ballast, reflectors, bulb brand and type, distance from water level.

you're better off following rex's concept of using lux per square inch (of surface area) http://www.rexgrigg.com/mlt.html if you really need some sort of guideline. downside of that is it is quite difficult to research how much lumens a certain bulb will produce, unless somebody out there has done testing.

if you really want an in-depth knowledge of lighting, read up on reefer forums. folks like Sanjay, The Grim Reefer, and Hahnmeister are very knowledgeable members at Reef Central. I believe PAR/PUR ratings are the most logical measurement at the moment

as for your tank, what did you mean by good light levels? just enough to keep plants alive? or do you want them growing at medium pace? or fast growth?
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post #3 of 4 (permalink) Old 10-17-2007, 10:47 PM
 
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CF with decent reflectors like a coralife fixture. So the WPG rule will work well for you.
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post #4 of 4 (permalink) Old 10-18-2007, 10:45 AM
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The WPG rule is based on NO T12 bulbs with a flat reflector.

And be careful because you are falling into the same trap.

Quote:
I found this chart on Wikipedia (http://en.wikipedia.org/wiki/Compact_fluorescent_lamp) that translates watt figure into lumens for different types of bulbs
so for example 60watt incandescent, 13 watt compact fluorescent and 30 watt Halogen bulbs all produce the same 865 lumens of light
That would be ONE particular incandescent bulb and ONE particular CF and ONE particular halogen bulb.

You can have two 55 watt CF bulbs and have a lumen difference of over 30%.
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