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[APD] Re: WPG rule

The biggest problem with the WPG rule of thumb is that
it doesn't work so well for small, really big tanks or
odd shaped tanks. 2x15w flourescents on a 10 gallon
tank is not the same quality 3wpg that you could
obtain using 40w tubes on a 4' tank. By small, I mean
less than 2'.

Power compact lighting simplfies the issue for smaller
tanks because you can get much better quality out of
the smaller tubes. Amano uses 7-10 WPG on his 10
gallon tanks and that's using PC's... FWIW, I find on
smaller tanks that the more light I use, the better
the plants look without any other changes. Algae isn't
a concern either.... 

On the flipside, with *really* big tanks, there seems
to be a critical intensity that we can reach and the
wpg rule seems to become less critical. I'd bet that's
more a function of depth and coverage than gallons...

No one seems to notice that coverage is really the
critical factor. As long as the tubes that best fit
the tank footprint are used, and you use enough to
create an even coverage of the top of the substrate,
it's enough light. Who cares how many watts they are
or how many exact gallons your tank is unless it's? 

I don't have any real experience with HID lighting, so
I'm only talking about the different flourescent

2 wpg of normal output flourescents on a tank over 18"
of height or if 15w bulbs are used is not nearly
enough unless you want to be very confined in plant

It's a lousy rule of thumb. 

John Wheeler   

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