View Full Version : WPG question
gman52
06-06-2005, 10:35 PM
this may seem like a dumb question, but i want to make sure i get it right. how do you find WPG. do u take the total wattage, and divide by the number of gallons the tank is
like this
40 watt bulb / 20 gallon tank = 2 WPG
thanks for help on dumb question
Yup, that is it. It applies best to NO fluorescents, other tube formats may need a bit of fudge factor (PC with a good reflector provides more light per watt and the reflector delivers more to the tank/plants).
Noddy65
06-07-2005, 1:38 AM
Continueing the dumb question theme:
What does NO fluorescents mean? And also PC (I assume its not Personal computer).
And one more: Does any one has any experience using those low voltage downlights you can by for your house (you know the ones that fit flush in the ceiling), they seem like a great idea. 150 w fitting for around $5 au, halide globes for about $1 au, attach it to a piece of wood, hang it above the tank and away you go. Does it seem too good to be true?
Mike
I believe NO means normal output. and PC is power compact.
Halides and such are not very efficient light sources compared to fluorescents, much of their wattage is wasted as heat.
slipknottin
06-07-2005, 12:07 PM
Halides and such are not very efficient light sources compared to fluorescents, much of their wattage is wasted as heat.
Ive found them to be pretty similar in efficiency, but HID's compact size means that the heat is radiated from a smaller place, and results in higher temperatures. Fluorescents spread that heat out along their entire length.
As far as I can tell the standard T12 40 watt bulb has a lumen output of ~3000. Giving a lumen/watt of 75.
A standard 175 watt MH has a lumen output of ~14,000. GIving a lumen/watt of 80.
There are of course, large variations in terms of color and lumen output as well. There are some MH bulbs with lumen/watt ratings of well over 120. And fluorescent bulbs can be significantly higher as well too, Im sure.
As we are on the aquatic plant forum, lumens don't mean a thing for plants, only for human eyes. The second most effective plant growth NO tube that I use for utility plant tanks is the Phillips "Daylight Deluxe" with the pathetic lumen rating of 2325 for the 40W T12s. Its CRI is nothing to write home about either at only 84. To my eyes it also the second most pleasing NO that I use. My first choice for displays is the Triton, which does not even advertise its ratings on those points.