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Old 10-16-2011, 05:24 PM   #6 (permalink)
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Default Re: PAR data collection

10 October 2011

Please fill out this form as completely as possible. Use a new form for each aquarium. You can also submit the information on the DFWAPC forum on Aquatic Plant Central and it will be immediately available for everyone.

Aquarium size 40 gallon, 36" x 15" x 16" tall
(gallons and dimensions)

Type of light fixture AND reflector 1 x 36” T5 NO dual bulb with original reflector (mirror polish)
1 x 24” T5 NO dual bulb with original reflector (mirror polish)
(power compact, T5 NO, metal halide, mirror polish reflector, white paint, mylar, etc.)

Number of lamps, bulbs, or tubes, and wattage 1 x 36” 10,000K 21 Watts
1 x 36” 6,700K 21 Watts
1 x 24” 10,000K 14 Watts
1 x 24” 6,700K 14 Watts
(examples: “2 T5 HO tubes, 24 w” or “1 metal halide 150 w”)

Age of lamps, bulbs, or tubes Average ~ 1 month except the 24” 10,000K which might be 3 years old

Other information
(brand, color temperature, spectrum, etc.)

Distance from light fixture to substrate 13”

PAR VALUES MEASURED AT SUBSTRATE: I am having trouble keeping any color except green in my tank, so my testing focused on how much light my glass top filters out.

@ substrate
Measurements with both fixtures: w/ glass 83, w/o glass 97
Measurements with only 36" lamp: w/ glass 48, w/o glass 54
Measurements with only 24" lamp: w/ glass 42, w/o glass 44

@ top (~ 1-2" below water line)
Measurements with both fixtures: w/ glass 365, w/o glass *
Measurements with only 36" lamp: w/ glass 281, w/o glass 303
Measurements with only 24" lamp: w/ glass 240, w/o glass 247

As you can see there isn't too much of a difference with or without the glass.

(Tip: you may want to measure PAR in several different locations. You can report multiple measurements, or calculate an average.)

Comments lights were arranged for optimum par values. Background of tank is overgrown and would skew results.
(Are there other conditions affecting light levels? What types of plants do you grow? Was the meter easy to use? Were you surprised by the results?)

Thank You!

*at 1-2" below the surface, there was not enough room for both lights to illuminate the same area. Most of the light from each lamp, because of the reflectors, is aimed straight down and I was unable to aim both at the sensor simultaneously.

I, also, just for fun measured, in roughly 2-3" increments, the par value from the substrate to the surface without the glass top using only the 36" fiture. These values are listed below.

Just under surface of water: 255
@ substrate: 52
directly under the light without any water: 609

Furthermore, for further reference to real sunlight: at 3:00 pm this afternoon I measured the sun in open air, and the meter showed about 2,000! A few inches below the water's surface in my pond values were still as high as 1,000.

Something else to add, I noticed something interesting involving the front glass of the tank. It seemed as though the glass would
reflect light back into the tank. Meaning I measured higher par values as I moved the sensor closer to the glass. If someone would confirm this, I would appreciate it. I'm not entirely sure my reflector aims straight down, so it might have something to do with this as well.

Last edited by Tex Gal; 10-22-2011 at 05:20 PM..
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