# WPG for T5 lighting



## tommyleestaples (Jan 4, 2010)

I have just bought a Juwel Vision 180 (46 Gallon) aquarium that comes with a 92 cm High Lite unit. It basically uses 2 x 35W T5 bulbs that are supposed to be the same length as T8 bulbs. One of the bulbs is 9000k & the other at 6800k. Both bulbs will have reflectors (If this makes any difference).

I basically want to grow live plants, I will be intially running the lights for 6 hours a day and slowly increasing over time. I will also be dosing with dry fertilizers, pressurized CO2 and will have a nutrient rich soil/substrate.

I want to be able to keep healthy (not fast growth as such) low/medium and would love to be able to grow high light red plants (but dont think this is possible).

I was working on the WPG rule however I understand that this method was based on the old T8/T12 bulbs. However if I am using (Higher intensity) T5 tubes then am I correct in thinking that the WPG rule will not apply. 

If this is the case, looking at the level of lighting I have, will I have low/medium or high light for plants. 

Would really appreciate your advice.


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## aquatic_clay (Aug 17, 2009)

Looks like you'll be in the middle of medium and high light. You might need to switch the 9000k out for another 6500k since 9000k can be a bit strong for plants.

clay


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## Newt (Apr 1, 2004)

You are correct in saying the WPG Rule was made up using T12/T10 (not T8) lighting. This never should have happened but bulbs are not rated on PAR value which would be a much better method of bulb comparison for aquarium application. Watts is a unit of electrical power used and came into being with the incandescent light bulbs. All company's bulbs were pretty much the same. A piece of tungsten filament in a vacuum. Watts consumption was dependent upon filament diameter/size. It was very easy to compare bulbs by watts with this style bulb. As more efficient fluorescent bulbs came into being the watts per gallon rule should have been chucked out the window but there was nothing to comapre it to. Alot of people will say lumens output but that only takes into account light mostly in the green area of the spectrum which plants dont utilize efficiently or at all for photosynthesis. It is a scale for the human eye that consists mainly of green that stimulates our eyes.

Additionally, you can find some T12 bulbs that will outperform/shine some T8s. Its all in the phosphor and cathode tube design that determines how intense the energy output is at a given nanometer.

A 54watt T5HO light bulb has about 25 to 30% more light output than a 55watt CF.

The kelvin value of a bulb doesnt affect plants from being too strong. Plant grow bulbs like the Sylvania GroLux is around 22,000K. Typically a higher kelvin bulb has more blue light being emitted.


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