Tropical Fish Keeping - Aquarium fish care and resources

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Busgod 04-19-2008 09:29 PM

lumens per square inch
Need someone who is smarter then I am to tell me if this is right:

I have a 55 gal corner tank It's radius is 27.5 inches by my calculations I have roughly 596 square inches of surface area.

i got this by this method( been forever since I was in school )

27.5 X 27.5 X 3.15159 = 2383.3899375 / 4 = 595.847484375

os here goes

596 X 22.43 / 79.4 = 168 watts of compact flourescent 6700k to 10000k
for very high light

I think I got it right (please corect me if I'm wrong )

okiemavis 04-19-2008 09:47 PM

Umm, I'm absolute crap with that kinda stuff. However, fish2all posted this link in another thread recently, and I found it extremely helpful. It calculates how much light you truly have based on your tank size, watts and the TYPE of light (ei T-5, compact florescent, etc).

Busgod 04-19-2008 09:53 PM

thanks mavis I got the lumens per watt from there just not sure that the math is right :D

herefishy 04-20-2008 12:40 AM

Lumens per watt is just a number to tell you the efficiency of your bulb and has no bearing on how much light.

I am currently trying to do a chart that will do away away with the watt per gallon myth. But I failed to take into consideration the number of bulbs on the market and getting technical data from manufacturers is a slow and tedious process.

At present, I have over 500 pages of technical data and sheets to process. That is on top of the calculations for each item at different specific depths of common aquariums. And I thought that I'd be done in two weeks, it's been almost 2 months now. lol

Lumens and spectral composition are the primary components in selecting a good bulb. Kelvins will also figure in to the equation, but not to the degree as lumens and spectrum. The primary concern is footcandles, the amount of light that reaches the plant, or work plane. All material has a light conductive coefficient. Water diffracts light and creates havoc when doing calculations. The deeper the tank, the more diffraction.

Don't mess with wattage unless you want to know the efficiency of the bulb.

Busgod 04-20-2008 01:19 AM

thanks herefishy I understand that there are all kinds of factors in lighting tank.

just looking to find out if i have the general idea right, as to the formula.

herefishy 04-20-2008 02:17 AM

Foot candles equation: Fc=Cp/(DxD)


Cp=candlepower of the bulb

D=distance of the work plane from the lamp

Remember that the one factor not present is spectrum. Proper spectrum is also needed for planted tanks.

roadracr 04-23-2008 04:37 PM

Busgod, your calculations start off in error. If you want to calculate area of a circle, it is simply Pi X (radius)^2. For some reason, you then divided this by four. Your area is actually the interim value of 2,384 square inches (actually you value for Pi was wrong - it's 3.14159, yielding 2,376 square inches, but who's counting?...)

Not sure what other logic you're using to calculate necessary lumens or watts required, but I think this answers your original question.

herefishy 04-23-2008 05:29 PM

roadracr, he's working with a corner tank not a cylinder. A corner tank is 1/4 of a cricle.

Busgod 04-23-2008 08:12 PM

thanks roadracer & herefishy and yes Its a corner tank not a circle.

so actually

27.5 X 27.5 X 3.14159= 2375.8274375 / 4 = 594

594 X 22.43 / 79.4 = 168

:D :D :D :BIGkissy:

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